{"id":22763,"date":"2024-10-07T11:47:41","date_gmt":"2024-10-07T06:17:41","guid":{"rendered":"https:\/\/samacheerkalvi.guide\/?p=22763"},"modified":"2024-10-08T09:47:43","modified_gmt":"2024-10-08T04:17:43","slug":"samacheer-kalvi-9th-science-guide-chapter-6","status":"publish","type":"post","link":"https:\/\/samacheerkalvi.guide\/samacheer-kalvi-9th-science-guide-chapter-6\/","title":{"rendered":"Samacheer Kalvi 9th Science Guide Chapter 6 Light"},"content":{"rendered":"

Tamilnadu State Board New Syllabus Samacheer Kalvi 9th Science Guide<\/a> Pdf Chapter 6 Light Text Book Back Questions and Answers, Notes.<\/p>\n

Tamilnadu Samacheer Kalvi 9th Science Solutions Chapter 6 Light<\/h2>\n

9th Science Guide Light Text Book Back Questions and Answers<\/h3>\n

I. Choose the correct answer :<\/span><\/p>\n

Question 1.
\nA ray of light passes from one medium to another medium. Refraction takes place when angle of incidence is
\n(a) 0\u00b0
\n(b) 45\u00b0
\n(c) 90\u00b0
\nAnswer:
\n(c) 90\u00b0<\/p>\n

\"Samacheer<\/p>\n

Question 2.
\nis used as reflectors in torchlight.
\n(a) Concave mirror
\n(b) Plane mirror
\n(c) Convex mirror
\nAnswer:
\n(a) Concave mirror<\/p>\n

Question 3.
\nWe can create enlarged, virtual images with
\n(a) concave mirror
\n(b) plane mirror
\n(c) convex mirror
\nAnswer:
\n(a) concave mirror<\/p>\n

\"Samacheer<\/p>\n

Question 4.
\nWhen the reflecting surface is curved outwards the mirror formed will be
\n(a) concave mirror
\n(b) convex mirror
\n(c) plane mirror
\nAnswer:
\n(b) convex mirror<\/p>\n

Question 5.
\nWhen a beam of white light passes through a prism it gets
\n(a) reflected
\n(b) only deviated
\n(c) deviated and dispersedAnswer:
\n(c) deviated and dispersed<\/p>\n

Question 6.
\nThe speed of light is maximum in
\n(a) vacuum
\n(b) glass
\n(c) diamond
\nAnswer:
\n(a) vacuum<\/p>\n

\"Samacheer<\/p>\n

II. State whether true or false. If false, correct the statement :<\/span><\/p>\n

1. The angle of deviation depends on the refractive index of the glass.
\nAnswer:
\nTrue<\/p>\n

2. If a ray of light passes obliquely from one medium to another, it does not suffer any deviation.
\nAnswer:
\nFalse.
\nCorrect statement: If a ray of light passes obliquely from one medium to another, it bends and from the normal.<\/p>\n

3. The convex mirror always produces a virtual, diminished and erect image of the object.
\nAnswer:
\nTrue.<\/p>\n

4. When an object is at the centre of curvature of concave mirror the image formed will be virtual and erect.
\nAnswer:
\nFalse.
\nCorrect statement: When an object is at the centre of curvature of concave mirror the image formed will be real and inverted.<\/p>\n

5. The reason for brilliance of diamonds is total internal reflection of light.
\nAnswer:
\nTrue.<\/p>\n

\"Samacheer<\/p>\n

III. Fill in the blanks :<\/span><\/p>\n

1. In going from a rarer to denser medium, the ray of light bends ……………………….
\nAnswer:
\ntowards the normal<\/p>\n

2. The mirror used in search light is ……………………….
\nAnswer:
\nconcave<\/p>\n

3. The angle of deviation of light ray in a prism depends on the angle of . ……………………….
\nAnswer:
\nincidence<\/p>\n

4. The radius of curvature of a concave mirror whose focal length is 5cm is ………………………..
\nAnswer:
\n10 cm<\/p>\n

5. Large ……………………….mirrors are used to concentrate sunlight to produce heat in solar furnaces.
\nAnswer:
\nconcave<\/p>\n

\"Samacheer<\/p>\n

IV. Match- the following :<\/span><\/p>\n\n\n\n\n\n\n\n
Ratio of height of image to height of object.<\/td>\nConcave mirror<\/td>\n<\/tr>\n
Used in hairpin bends in mountains.<\/td>\nTotal internal reflection<\/td>\n<\/tr>\n
Coin inside water appearing slightly raised.<\/td>\nMagnification<\/td>\n<\/tr>\n
Mirage<\/td>\nConvex mirror<\/td>\n<\/tr>\n
Used as Dentist\u2019s mirror.<\/td>\nRefraction<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

Answer:<\/p>\n\n\n\n\n\n\n\n
Ratio of height of image to height of object.<\/td>\nMagnification<\/td>\n<\/tr>\n
Used in hairpin bends in mountains.<\/td>\nConvex mirror<\/td>\n<\/tr>\n
Coin inside water appearing slightly raised.<\/td>\nRefraction<\/td>\n<\/tr>\n
Mirage<\/td>\nTotal internal reflection<\/td>\n<\/tr>\n
Used as Dentist\u2019s mirror.<\/td>\nConcave mirror<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

V. Assertion & Reason :<\/span><\/p>\n

Mark the correct choice as:
\n(a) If both assertion and reason are true and reason is the correct explanation.
\n(b) If both assertion and reason are true and reason is not the correct explanation.
\n(c) If assertion is true but reason is false.
\n(d) If assertion is false but reason is true<\/p>\n

\"Samacheer<\/p>\n

Question 1.
\nAssertion: For observing the traffic at a hairpin bend in mountain paths a plane mirror is preferred over the convex mirror and concave mirror.
\nReason: A convex mirror has a much larger field of view than a plane mirror or a . concave mirror.
\nAnswer:
\n(d) Assertion is false but reason is true<\/p>\n

Question 2.
\nAssertion: The incident ray is directed towards the centre of curvature of spherical mirror. After reflection it retraces its path.
\nReason : Angle of incidence (i) = Angle of reflection (r) = 0\u00b0.
\nAnswer:
\n(a) Both assertion and reason are true and reason is the correct explanation<\/p>\n

VI. Answer very briefly:<\/span><\/p>\n

Question 1.
\nAccording to cartesian sign convention, which mirror and which lens has negative focal length?
\nAnswer:
\nConcave mirror is having a negative focal length.<\/p>\n

\"Samacheer<\/p>\n

Question 2.
\nName the mirror(s) that can give (i) an erect and enlarged image, (ii) same sized, inverted image.
\nAnswer:
\nConcave mirror.<\/p>\n

Question 3.
\nIf an object is placed at the focus of a concave mirror, where is the image formed?
\nAnswer:
\nThe image will be formed at infinity as real and inverted.<\/p>\n

Question 4.
\nWhy does a ray of light bend when it travels from one medium to another?
\nAnswer:
\nA ray of light bend when it travels from one medium to another due to the change in velocity of light in two different medium.<\/p>\n

Question 5.
\nWhat is the speed of light in vacuum?
\nAnswer:
\nThe speed of light in vacuum is known to be almost exactly 300,000 km per second. In 1665 the Danish astronomer Ole Roemer first estimated the speed of light by observing one of the twelve moons of the planet Jupiter.<\/p>\n

\"Samacheer<\/p>\n

Question 6.
\nConcave mirrors are used by dentists to examine teeth. Why?
\nAnswer:
\nAs concave mirror produces virtual, erect and magnified images when an object is placed in<\/p>\n

VII. Answer briefly :<\/span><\/p>\n

Question 1.
\na) Complete the diagram to show how a concave mirror forms the image of the object.
\nb) What is the nature of the image?
\n\"Samacheer
\nAnswer:
\na)
\n\"Samacheer<\/p>\n

\"Samacheer
\nb) Real, inverted and magnified.<\/p>\n

Question 2.
\nPick out the concave and convex mirrors from the following and tabulate them. Rear-view mirror, Dentist\u2019s mirror, Torch-light mirror, Mirrors in shopping malls, Make-up mirror.
\nAnswer:<\/p>\n\n\n\n\n\n\n
Concave Mirror<\/td>\nConvex Mirror<\/td>\n<\/tr>\n
Dentist\u2019s mirror<\/td>\nRearview mirror<\/td>\n<\/tr>\n
Torchlight mirror<\/td>\nMirrors in shopping malls<\/td>\n<\/tr>\n
Makeup mirror<\/td>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

Question 3.
\nState the direction of the incident ray which after reflection from a spherical mirror retraces its path. Give a reason for your answer.
\nAnswer:
\nWhen an incident ray is directed towards the centre of curvature, at all the points of the spherical mirror, the ray is always normal. Therefore, angle of incidence i = Angle of reflection r = 0\u00b0.<\/p>\n

Question 4.
\nWhat is meant by magnification? Write its expression. What is its sign for real image and virtual image?
\nAnswer:
\nMagnification is the increase in size of an image compared to true size.
\n\"Samacheer
\n(a) Negative sign – real image
\n(b) Positive sign – virtual image<\/p>\n

\"Samacheer<\/p>\n

Question 5.
\nWrite the spherical mirror formula and explain the meaning of each symbol used in it.
\nAnswer:
\nThe expression relating the distance of the object u, distance of image v and focal length\/of a spherical mirror is called the mirror equation. It is given as:
\nMirror formula: \\(\\frac{1}{f}=\\frac{1}{u}+\\frac{1}{v}\\)
\nHere, f – focal length of spherical mirror; u – distance of the objective; v – distance of the image.<\/p>\n

VIII. Answer in detail :<\/span><\/p>\n

Question 1.
\na) Draw ray diagrams to show how the image is formed using a concave mirror, when the position of objeict is (i) at C (ii) between C and F (iii) between F and P of the mirror.
\nb) Mention the position and nature of image in each case.
\nAnswer:
\na) object At C
\ni)
\n\"Samacheer
\n(b) Position of an object: At C
\nPosition of the image: At C<\/p>\n

Nature of the image:
\n(i) Real
\n(ii) Inverted
\n(iii) Same size as the object<\/p>\n

(ii) object At C and F
\n\"Samacheer
\nPosition of the object: Between C and F
\nPosition of the image: Beyond C<\/p>\n

Nature of the image :
\n(i) Real
\n(ii) Inverted
\n(iii) Magnified<\/p>\n

(iii) Object between F and P of the Mirror
\n\"Samacheer
\nPosition of object : Between F and P
\nPosition of the image : Behind the Mirror<\/p>\n

Nature of the image :
\n(i) Virtual
\n(ii) Erect
\n(iii) Magnified<\/p>\n

\"Samacheer<\/p>\n

Question 2.
\nExplain with diagrams how refraction of incident light takes place from a) rarer to denser medium b) denser to rarer medium c) normal to the surface separating the two media.
\nAnswer:
\na) rarer to denser medium
\nWhen a ray of light travels from optically rarer medium to optically denser medium, it bends towards the normal.
\n\"Samacheer<\/p>\n

b) denser to rarer medium
\nWhen a ray of light from an optically denser medium to an optically rarer medium it bends away from the normal.
\n\"Samacheer<\/p>\n

c) normal to the surface separating the two media.
\nA ray of light incident normally on a denser medium it goes without any deviation.
\n\"Samacheer<\/p>\n

\"Samacheer<\/p>\n

IX. Numerical Problems:<\/span><\/p>\n

Question 1.
\nA concave mirror produces three times magnified real image of an object placed at 7 cm in front of it. Where is the image located?
\nAnswer:
\nHere given magnification m = 3
\nObject distance u = -7 cm
\nMagnification m = \\(-\\frac{v}{u}\\) Real image
\n-3 = \\(-\\frac{v}{u}\\)
\n3u = -v
\nv = 3u = 3 x 7 = 21 cm
\nThe image will be formed at a distance of 21 cm in front of concave mirror from its pole.<\/p>\n

Question 2.
\nLight enters from air into a glass plate having a refractive index of 1.5. What is the speed of light in glass?
\nAnswer:
\nRefractive index of a glass plate \u03bc = 1.5
\nSpeed of light in vacuum is C = 3 x 108<\/sup>ms-1<\/sup>
\nSpeed of light in glass V =?
\n\"Samacheer
\nspeed of light in glass = 2 \u00d7 108<\/sup>ms-1<\/sup><\/p>\n

\"Samacheer<\/p>\n

Question 3.
\nThe speed of light in water is 2.25 \u00d7 108<\/sup>ms-1<\/sup>. If the speed of light in a vacuum is 3 \u00d7 108<\/sup>ms-1<\/sup>, calculate the refractive index of water.
\nAnswer:
\nSpeed of light in water V = 2.25 \u00d7 108<\/sup>ms-1<\/sup>
\nSpeed of light in vacuum C = 3 \u00d7 108<\/sup>ms-1<\/sup>
\nRefractive index of water \u03bc =?
\n\"Samacheer<\/p>\n

X. Higher Order Thinking Skills.<\/span><\/p>\n

Question 1.
\nLightray emerges from water into the air. Draw a ray diagram indicating the change in its path in the water.
\nAnswer:
\n\"Samacheer<\/p>\n

\"Samacheer<\/p>\n

Question 2.
\nWhen a ray of light passes from air into glass, is the angle of refraction greater than or less than the angle of incidence?
\nAnswer:
\nLight bends towards the normal because glass is denser than air.
\nIt bends towards normal since light has to travel with the lesser speed in the glass but within a short time.
\nr < i. The angle of refraction is less than the angle of incidence.<\/p>\n

Question 3.
\nWhat do you conclude about the speed of light in diamond, if the refractive index of diamond is 2.41?
\nAnswer:
\nRefractive index of diamond \u03bc = 2.41
\n\"Samacheer
\n\u2234 Speed of light in a diamond (1.24 \u00d7 108<\/sup>ms-1<\/sup>) is less than the speed of light in air (3 \u00d7 108<\/sup>ms-1<\/sup>).
\nThe refractive index of diamond is 2.42, it means that speed of light in air (vacuum) is 2.42 times the speed of light in a diamond.<\/p>\n

Intext Activities<\/strong><\/p>\n

ACTIVITY – 1<\/span><\/p>\n

Stand before the mirror in your dressing table or the mirror fixed in a steel almirah. Do you see your whole body? To see your entire body in a mirror, the mirror should be atleast half of your height. Height of the mirror= Your height\/2.
\nSolution :
\n(i) If the height of a person is 5 feet, then he should use a plane mirror of 2Vi feet height and fix in a steal almirah.
\n(ii) Now if he stand before it his full body will be seen on the mirror because hight of the mirror = \\(\\frac{\\text { Our hieight }}{2}\\)<\/p>\n

\"Samacheer<\/p>\n

ACTIVITY – 2<\/span><\/p>\n

Hold a concave mirror in your hand (or place it in a stand). Direct its reflecting surface towards the sun. Direct the light reflected by the mirror onto a sheet of paper held not very far from the mirror. Move the sheet of paper back and forth gradually until you find a bright, sharp spot of light on the paper. Position the mirror and the paper at the same location for few moments. What do you observe? Why does the paper catch fire?
\nSolution :
\nA concave mirror converges all the light rays coming from the Sun. All these light rays converge and meet at the focus of the mirror.
\nSo, all the heat and light is focused on the principal focus (F). When a paper is kept at the focus (F), it starts burning, as this point is very hot.<\/p>\n

ACTIVITY – 3<\/span><\/p>\n

Take a convex mirror. Hold it in one hand. Hold a pencil close to the mirror in the upright position in the other hand. Observe the image of the pencil in the mirror. Is the image erect or inverted? Is it diminished or enlarged? Move the pencil slowly away from the mirror. Does the image become smaller or larger? What do you observe?
\n\"Samacheer
\nSolution :<\/p>\n

    \n
  1. When a pencil is held in the upright position in front of a convex mirror, its diminished, erect image is formed which is virtual and therefore seen in the convex mirror.<\/li>\n
  2. When the pencil is moved away from the convex mirror size of image becomes smaller and smaller but image remains erect.<\/li>\n
  3. As we move away, the object from the convex mirror, image shifts towards the focus.<\/li>\n<\/ol>\n

    \"Samacheer<\/p>\n

    ACTIVITY – 4<\/span><\/p>\n

    Refraction of light at air-water interface
    \nPut a straight pencil into a tank of water or beaker of water at an angle of 45\u00b0 and look at it from one side and above. How does the pencil look now?
    \nThe pencil appears to be bent at the surface of water.
    \nSolution :
    \n\"Samacheer
    \nBoth the above activities are the result of refraction of light. The bending of light rays when they pass obliquely from one medium to another medium is called refraction of light.<\/p>\n

    9th Science Guide Light Additional Important Questions and Answers<\/h3>\n

    I. Choose the correct answer :<\/span><\/p>\n

    Question 1.
    \nA ray of light is incident towards a plane mirror at an angle of 30\u00b0 with the mirror surface. What will be the angle of reflection?
    \n(a) 45\u00b0
    \n(b) 30\u00b0
    \n(c) 90\u00b0
    \n(d) 60\u00b0
    \nAnswer:
    \n(d) 60\u00b0<\/p>\n

    \"Samacheer<\/p>\n

    Question 2.
    \nA 10 mm long bin is placed vertically in front of a concave mirror. A 5 mm long image of the bin is formed at 30 cm in front of the mirror. The focal length of this mirror is
    \n(a) -20cm
    \n(b) -30cm
    \n(c) -60cm
    \n(d) -40cm
    \nAnswer:
    \n(a) – 20cm<\/p>\n

    Question 3.
    \nA ray of light as it travels from medium A to medium B refractive index of the medium B relative to medium A is (\u03bcB\/ \u03bcA)
    \n(a) \\(\\frac{\\sqrt{3}}{\\sqrt{2}}\\)
    \n(b) \\(\\frac{\\sqrt{2}}{\\sqrt{3}}\\)
    \n(c) \\(\\frac{{1}}{\\sqrt{2}}\\)
    \n(d) \\(\\sqrt{2}\\)
    \nAnswer:
    \n(b) \\(\\frac{\\sqrt{2}}{\\sqrt{3}}\\)<\/p>\n

    \"Samacheer<\/p>\n

    Question 4.
    \nUnder which of the following conditions a concave mirror can form an image larger than the actual object?
    \n(a) when the object is kept at a distance equal to its radius of curvature.
    \n(b) when object is kept at a distance less than its focal length.
    \n(c) when object is placed between the focus and centre of curvature
    \n(d) when object is kept at a distance greater than its radius of curvature.
    \nAnswer:
    \n(c) when object is placed between the focus and centre of curvature<\/p>\n

    Question 5.
    \nIn torches, searchlights and head lights of vehicles the bulb is placed …………………………… of the concave mirror.
    \n(a) between and F of the reflector
    \n(b) Very near to F
    \n(c) between F & C
    \n(d) at C
    \nAnswer:
    \n(b) Very near to F<\/p>\n

    Question 6.
    \nA boy is standing at a distance of 3m in front of a plane mirror. The distance between the boy and his image is ………………….. m
    \n(a) 4
    \n(b) 2
    \n(c) 3
    \n(d) 6
    \nAnswer:
    \n(c) 3<\/p>\n

    \"Samacheer<\/p>\n

    Question 7.
    \nThe image formed by a concave mirror is real, inverted and of the same size as that of the object the position of the object should be
    \n(a) beyond C
    \n(b) between C & F
    \n(c) at C
    \n(d) at F
    \nAnswer:
    \n(c) at C<\/p>\n

    Question 8.
    \nWhich of the following has the highest refractive index
    \n(a) air
    \n(b) water
    \n(c) diamond
    \n(d) glass
    \nAnswer:
    \n(c) diamond<\/p>\n

    Question 9.
    \nThe image formed by a plane mirror is
    \n(a) real
    \n(b) diminished
    \n(c) enlarged
    \n(d) laterally inverted
    \nAnswer:
    \n(d) laterally inverted<\/p>\n

    \"Samacheer<\/p>\n

    Question 10.
    \nThe incident ray passing through ‘F of a mirror ………………….. after reflection
    \n(a) passes through C
    \n(b) passes through F
    \n(c) passes parallel to the principal axis
    \n(d) passes through the pole
    \nAnswer:
    \n(c) passes parallel to the principal axis<\/p>\n

    Question 11.
    \nThe incident ray passing through C of a mirror ………………….. after reflection.
    \n(a) passes through C
    \n(b) passes through F
    \n(c) passes through P
    \n(d) parallel to the principal axis
    \nAnswer:
    \n(a) passes through C<\/p>\n

    Question 12.
    \nThe incident ray parallel to the principal axis of a mirror ………………….. after reflection.
    \n(a) passes through C
    \n(b) passes through F
    \n(c) passes through P
    \n(d) reverts back in the opposite direction
    \nAnswer:
    \n(b) passes through F<\/p>\n

    \"Samacheer<\/p>\n

    Question 13.
    \nAccording to sign convention the distance of the object.
    \n(a) is always positive
    \n(b) is always negative
    \n(c) maybe positive or negative
    \n(d) is equal to object height.
    \nAnswer:
    \n(b) is always negative<\/p>\n

    Question 14.
    \nAccording to sign convention the distance of the image.
    \n(a) is always positive
    \n(b) is always negative
    \n(c) maybe positive or negative
    \n(d) is equal to image height
    \nAnswer:
    \n(c) maybe positive or negative<\/p>\n

    Question 15.
    \nTotal internal reflection will occur if the angle of reflection is
    \n(a) 45\u00b0
    \n(b) 60\u00b0
    \n(c) 90\u00b0
    \n(d) 99\u00b0
    \nAnswer:
    \n(d) 99\u00b0<\/p>\n

    \"Samacheer<\/p>\n

    Question 16.
    \nMagnification for the………………….. image is always …………………..
    \n(a) real, positive
    \n(b) real, negative
    \n(c) virtual, negative
    \n(d) virtual, positive
    \nAnswer:
    \n(b) real, negative<\/p>\n

    Question 17.
    \nIf magnification is +1.5. The image is …………………..
    \n(a) erect
    \n(b) diminished
    \n(c) real
    \n(d) invected
    \nAnswer:
    \n(a) erect<\/p>\n

    Question 18.
    \nThe refractive index of a denser medium with respect to rarer medium is
    \n(a) 1
    \n(b) greater than 1
    \n(c) less than 1
    \n(d) negative
    \nAnswer:
    \n(b) greater than 1<\/p>\n

    \"Samacheer<\/p>\n

    Question 19.
    \nWe can see objects because of
    \n(a) reflection
    \n(b) refraction
    \n(c) transmission
    \n(d) diffraction
    \nAnswer:
    \n(a) reflection<\/p>\n

    Question 20.
    \nThe image formed by a convex mirror is always
    \n(a) real (b) enlarged
    \n(c) virtual & enlarged
    \n(d) diminished
    \nAnswer:
    \n(d) diminished<\/p>\n

    \"Samacheer<\/p>\n

    Question 21.
    \nAs you move an object always from a convex mirror, its image becomes…………………..
    \nand moves towards
    \n(a) smaller, infinity
    \n(b) smaller, focus
    \n(c) enlarged, infinity
    \n(d) enlarged, focus
    \nAnswer:
    \n(b) smaller, focus<\/p>\n

    Question 22.
    \nFor a spherical mirror ………………….. is true.
    \n(a) f = 2R
    \n(b) R = 2f
    \n(c) fR = 2
    \n(d) fR = \\(\\frac { 1 }{ 2 }\\)
    \nAnswer:
    \n(b) R = 2f<\/p>\n

    \"Samacheer<\/p>\n

    Question 23.
    \nThe mirror formula is…………………..
    \n\"Samacheer
    \nAnswer:
    \n(c) \\(\\frac{1}{f}=\\frac{1}{u}+\\frac{1}{v}\\)<\/p>\n

    Question 24.
    \nFor a plane mirror, magnification m =
    \n(a) 0
    \n(b) 1
    \n(c) \u00b1 1
    \n(d) \u22640
    \nAnswer:
    \n(b) 1<\/p>\n

    Question 25.
    \nMagnification for convex mirror is
    \n(a) always positive
    \n(b) always negative
    \n(c) some times positive
    \n(d) 1
    \nAnswer::
    \n(a) always positive<\/p>\n

    Question 26.
    \nIf the angle of incidence i = 0, the angle of reflection r =
    \n(a) 0\u00b0
    \n(b) 90\u00b0
    \n(c) 180\u00b0
    \n(d) 45\u00b0
    \nAnswer:
    \n(a) 0\u00b0<\/p>\n

    \"Samacheer<\/p>\n

    Question 27.
    \nRefractive index of a medium is …………………..
    \n(a) speed of light in air to speed of light in vacuum
    \n(b) speed of light in vacuum to speed of light in air
    \n(c) focal length to object distance
    \n(d) speed of light in the medium \u00d7 speed of light in the air
    \nAnswer:
    \n(a) speed of light in air to speed of light in vacuum<\/p>\n

    Question 28.
    \nBending of light as it passes from one medium to another is called
    \n(a) reflection
    \n(b) diffraction
    \n(c) refraction
    \n(d) deviation
    \nAnswer:
    \n(c) refraction<\/p>\n

    Question 29.
    \nRatio of sine of angle of incidence to sine of angle of refraction is ………………….
    \n(a) gravitational law
    \n(b) law of reflection
    \n(c) law of refraction
    \n(d) snell\u2019s law.
    \nAnswer:
    \n(d) snell\u2019s law<\/p>\n

    \"Samacheer<\/p>\n

    Question 30.
    \nEntire light is reflected back into denser medium is called
    \n(a) total internal reflection
    \n(b) refraction
    \n(c) reflection
    \n(d) total external refraction.
    \nAnswer:
    \n(a) total internal reflection<\/p>\n

    Question 31.
    \nOuter concentric shell in optic fiber is called
    \n(a) cladding
    \n(b) core
    \n(c) mantel
    \n(d) coat
    \nAnswer:
    \n(a) cladding<\/p>\n

    Question 32.
    \nWhen light is going from a denser to a less dense medium, the critical angle is the angle of incidence for which the angle of refraction is
    \n(a) 48\u00b0
    \n(b) 90\u00b0
    \n(c) 42\u00b0
    \n(d) 51\u00b0
    \nAnswer:
    \n(b) 90\u00b0<\/p>\n

    Question 33.
    \nA bundle of glass threads, each of which is capable of transmitting messages using light waves is called
    \n(a) microscope
    \n(b) convex
    \n(c) periscope
    \n(d) optic fibre
    \nAnswer:
    \n(d) optic fibre<\/p>\n

    \"Samacheer<\/p>\n

    Question 34.
    \nA ray of light travelling in medium 1 strikes and travels into another transparent medium 2. If the speed of light is greater in medium 1, the ray will
    \n(a) refract towards the normal
    \n(b) have an angle of incidence smaller than be angle of refraction
    \n(c) refract away from the normal
    \n(d) undergo total internal reflection
    \nAnswer:
    \n(a) refract towards the normal<\/p>\n

    Question 35.
    \nA ray of light travels from air into a glass block as shown. It makes an angle of 30\u00b0 with the surface of the block. If the refractive index of the glass is 1.5, what will be the angle of refraction?
    \n\"Samacheer
    \n(a) 35.26\u00b0
    \n(b) 1.30\u00b0
    \n(c) 48.59\u00b0
    \n(d) 19.47\u00b0
    \nAnswer:
    \n(d) 19.47\u00b0<\/p>\n

    Question 36.
    \nThe field of view is maximum for …………………
    \n(* FOV is the extent of the observable area that is seen at any given instant)
    \n(a) plane mirror
    \n(b) concave mirror
    \n(c) convex mirror
    \nAnswer:
    \n(c) convex mirror<\/p>\n

    \"Samacheer<\/p>\n

    Question 37.
    \nA real and enlarged image can be obtained by using a
    \n(a) convex mirror
    \n(b) plane mirror
    \n(c) concave mirror
    \nAnswer:
    \n(c) concave mirror<\/p>\n

    Question 38.
    \nWhich of the following statements about total internal reflection is true?
    \n(a) angle of incidence should be greater than the critical angle
    \n(b) light must travel from a medium of higher refractive index to a medium of lower refractive index
    \n(c) both (a) and (b)
    \nAnswer:
    \n(c) both (a) and (b)<\/p>\n

    Question 39.
    \nThe focal length of a concave mirror is 5cm. Its radius of curvature is
    \n(a) 5 cm
    \n(b) 10 cm
    \n(c) 2.5 cm
    \nAnswer:
    \n(b) 10 cm<\/p>\n

    \"Samacheer<\/p>\n

    II. Fill in the blanks :<\/span><\/p>\n

    1. The ratio of the sine of the angle of incidence to the sine of …………………is constant.
    \nAnswer:
    \nangle of refraction<\/p>\n

    2. A spherical mirror whose reflecting surface is curved outwards is called ………………… mirror.
    \nAnswer:
    \nconvex<\/p>\n

    3. All distances parallel to the principal axis are measured from the ………………… of the
    \nmirror.
    \nAnswer:
    \npole<\/p>\n

    4. A negative sign in the value of magnification indicates that the image is …………………
    \nAnswer:
    \nreal<\/p>\n

    5. Light is refracted or bent while going from one medium to another because of its ………………… changes.
    \nAnswer:
    \nspeed<\/p>\n

    \"Samacheer<\/p>\n

    III. State whether true or false. If false, correct the statement:<\/span><\/p>\n

    1. The critical angle is defined as the angle of incidence at which the total internal reflection starts to occur.
    \nAnswer:
    \nTrue.<\/p>\n

    2. The angle of incidence is equal to the angle of reflection for perfect reflection.
    \nAnswer:
    \nTrue.<\/p>\n

    3. The image formed in a plane mirror is always inverted.
    \nAnswer:
    \nFalse.
    \nCorrect statement: The image formed in a plane mirror is always erect.<\/p>\n

    4. A star appears twinkling into the sky because of the reflection of light by the atmosphere
    \nAnswer:
    \nFalse.
    \nCorrect statement: A star appears twinkling into the sky because of the refraction of light by the atmosphere.<\/p>\n

    5. Mirage is an example of refraction and total internal reflection of light.
    \nAnswer:
    \nTrue.<\/p>\n

    \"Samacheer<\/p>\n

    6. Optical Fibres are based on the phenomenon of dispersion
    \nAnswer:
    \nFalse.
    \nCorrect statement: Optical Fibres are based on total internal reflection.<\/p>\n

    7. A water tank appears shallower when it is viewed from the top due to refraction.
    \nAnswer:
    \nTrue.<\/p>\n

    8. Twinkling of stars and Mirage are the two phenomena occurring due to refraction.
    \nAnswer:
    \nTrue.
    \nTwinkling of stars and Mirage.<\/p>\n

    9. Angle of incidence is zero if a ray of light is incident normal to be surface separating the low media.
    \nAnswer:
    \nTrue.<\/p>\n

    10. A real image is inverted and can be caught on the screen.
    \nAnswer:
    \nTrue.<\/p>\n

    11. The minimum length of the mirror required to see the full image of the person is half ‘ of his height.
    \nAnswer:
    \ntrue.<\/p>\n

    \"Samacheer<\/p>\n

    12. The pencil appears to be bent at the surface of the water is due to refraction.
    \nAnswer:
    \nTrue.<\/p>\n

    13. The speed of light decreases in a denser medium, light bends towards the normal.
    \nAnswer:
    \nTrue.<\/p>\n

    14. If the object is at infinity in front of a convex mirror the image is formed at infinity.
    \nAnswer:
    \nFalse.
    \nCorrect statement: The image is formed at F, behind the mirror<\/p>\n

    15. An object is placed at a distance of 3cm from a plane mirror. The distance of the object and image is 3cm.
    \nAnswer:
    \nFalse.
    \nCorrect statement: The distance of the object and image is 6 cm.<\/p>\n

    16. The distance from centre of curvature of the mirror to the pole is called the focal length of the mirror.
    \nAnswer:
    \nFalse.
    \nCorrect statement: The distance between the centre of the mirror and the focal point of the mirror is called the focal length of a mirror.<\/p>\n

    \"Samacheer<\/p>\n

    17. Light is one of the slowest travelling energy with a speed of 3 \u00d7 10-8<\/sup>ms-1<\/sup>
    \nAnswer:
    \nFalse.
    \nCorrect statement : (Light is one of the fastest travelling energy with a speed of 3 \u00d7 10-8<\/sup>ms-1<\/sup><\/p>\n

    18. The angle of incidence at which the angle of refraction is Q\u00a3 is called the critical angle.
    \nAnswer:
    \nFalse.
    \nCorrect statement: The angle of incidence at which the angle of refraction is 90\u00b0 is called the critical angle.<\/p>\n

    IV. Match the following :<\/span><\/p>\n

    Question 1.<\/p>\n\n\n\n\n\n\n\n
    Column I<\/td>\nColumn II<\/td>\n<\/tr>\n
    (i) A plane mirror<\/td>\n(a) Image is erect & smaller in size than the object.<\/td>\n<\/tr>\n
    (ii) A concave mirror<\/td>\n(b) Image is erect & of the same size as of the object.<\/td>\n<\/tr>\n
    (iii) A convex<\/td>\n(c) Used by dentists to see an enlarged images of teeth.<\/td>\n<\/tr>\n
    <\/td>\n(d) Can form images of objects spread over a large area.<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

    Answer:<\/p>\n\n\n\n\n\n\n
    Column I<\/td>\nColumn II<\/td>\n<\/tr>\n
    (i) A plane mirror<\/td>\n(b) Image is erect & of the same size as of the object.<\/td>\n<\/tr>\n
    (ii) A concave mirror<\/td>\n(c) Used by dentists to see enlarged image of teeth.<\/td>\n<\/tr>\n
    (iii) A convex<\/td>\n(d) Can form image of objects spread over a large area.<\/span><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

    Question 2.<\/p>\n\n\n\n\n\n\n
    Column I<\/td>\nColumn II<\/td>\n<\/tr>\n
    (i) r > 90<\/td>\n(a) Light gazes the surface of separation between two mode.<\/td>\n<\/tr>\n
    (ii) r = 90<\/td>\n(b) No refraction.<\/td>\n<\/tr>\n
    (iii) r < 90<\/td>\n(c) Refracted ray away from the normal<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

    Answer:<\/p>\n\n\n\n\n\n\n
    Column I<\/td>\nColumn II<\/td>\n<\/tr>\n
    (i) r > 90<\/td>\n(b) No refraction.<\/td>\n<\/tr>\n
    (ii) r = 90<\/td>\n(a) Light gazes the surface of separation between two mode.<\/td>\n<\/tr>\n
    (iii) r < 90<\/td>\n(c) Refracted ray away from the normal<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

    \"Samacheer<\/p>\n

    Question 3.<\/p>\n\n\n\n\n\n\n\n\n
    Column I<\/td>\nColumn II<\/td>\n<\/tr>\n
    (i) plane mirror<\/td>\n(a) Focal length is positive.<\/td>\n<\/tr>\n
    (ii) concave<\/td>\n(b) Focal length is negative.<\/td>\n<\/tr>\n
    (iii) convex<\/td>\n(c) Focal length is infinity.<\/td>\n<\/tr>\n
    (iv) Real image<\/td>\n(d) Magnification if positive value.<\/td>\n<\/tr>\n
    (v) Virtual image<\/td>\n(e) Magnification if negative value.<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

    Answer:<\/p>\n\n\n\n\n\n\n\n\n
    Column I<\/td>\nColumn II<\/td>\n<\/tr>\n
    (i) plane mirror<\/td>\n(c) Focal length is infinity.<\/td>\n<\/tr>\n
    (ii) concave<\/td>\n(b) Focal length is negative.<\/td>\n<\/tr>\n
    (iii) convex<\/td>\n(a) Focal length is positive.<\/td>\n<\/tr>\n
    (iv) Real image<\/td>\n(e) Magnification if negative value.<\/td>\n<\/tr>\n
    (v) Virtual image<\/td>\n(d) Magnification if positive value.<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

    Question 4.
    \n\"Samacheer
    \nAnswer:
    \n\"Samacheer<\/p>\n

    V. Assertion & Reason Type :<\/span><\/p>\n

    (a) If both assertion & reason are true and the reason is the correct explanation of the assertion.
    \n(b) If both assertion & reason are true but the reason is not correct explanation of the assertion.
    \n(c) If assertion is true but reason is false.
    \n(d) If assertion & reason both are false.
    \n(e) If assertion is false but reason is true.<\/p>\n

    \"Samacheer<\/p>\n

    Question 1.
    \nAssertion : The air bubble shines in water.
    \nReason : Air bubble shines due to refraction of light.
    \nAnswer:
    \n(c) If assertion is true but reason is false<\/p>\n

    Question 2.
    \nAssertion : The focal length of the mirror is \/and distance of the object from the
    \nfocus is V then the magnification of the mirror will be \\(\\left(\\frac{f}{f-u}\\right)\\)
    \n\"Samacheer
    \nAnswer:
    \n(a) Both assertion & reason are true and the reason is the correct explanation of the assertion<\/p>\n

    Question 3.
    \nAssertion : When an object is placed between two plane mirrors, then all the images found are of equal brightness.
    \nReason : Only two images are obtained in case of plane-parallel mirrors.
    \nAnswer:
    \n(d) Assertion & reason both are false<\/p>\n

    \"Samacheer<\/p>\n

    Question 4.
    \nAssertion: The mirrors used in torch lights are parabolic not concave.
    \nReason: The image formed by concave mirror is always virtual.
    \nAnswer:
    \n(c) Assertion is true but reason is false<\/p>\n

    Question 5.
    \nAssertion : The nature of the image depends on the size of the mirror.
    \nReason : Small mirrors always form a virtual image.
    \nAnswer:
    \n(d) Assertion & reason both are false<\/p>\n

    Question 6.
    \nAssertion : A real image cannot be produced by plane or convex mirror.
    \nReason : The focal length of a convex mirror is always taken as possitive.
    \nAnswer:
    \n(e) Assertion is false but reason is true<\/p>\n

    \"Samacheer<\/p>\n

    VI. Answer very briefly :<\/span><\/p>\n

    Question 1.
    \nWhich is optically denser out of the two medium M1<\/sub>& M2<\/sub> having the refractive indices = 1.71 and 1.36 respectively?
    \nAnswer:
    \nM1<\/sub>
    \nReason: Optical density increases as the value of the refractive index increases.<\/p>\n

    Question 2.
    \nTwo medium with refractive index 1.31 & 1.50 is given. In which case (i) Bending of light is more and (ii) speed of light is more.
    \nAnswer:
    \n(i) 1.50 – Bending is more
    \n(ii) 1.31 – Speed is more<\/p>\n

    \"Samacheer<\/p>\n

    Question 3.
    \nUnder what circumstances there won\u2019t be any refraction of light when it enters from one medium to another?
    \nAnswer:<\/p>\n

      \n
    • When light incident at 90\u00b0, it will not bend.<\/li>\n
    • When light passes from denser medium to rarer medium and if it is incident at an angle greater than the critical angle, it will reflect but will not refract.<\/li>\n<\/ul>\n

      Question 4.
      \nA ray of light traveling in air enters obliquely into water. Does the light ray bend towards the normal or away from the normal? Why?
      \nAnswer:<\/p>\n

        \n
      • When a ray of light travels from air into water obliquely, it bends towards the normal.<\/li>\n
      • This is because water is optically denser than air.<\/li>\n
      • On entering water, speed of light decreases and the light bends towards normal.<\/li>\n<\/ul>\n

        Question 5.
        \nList down the uses of concave mirror.
        \nAnswer:
        \nConcave mirrors are used :<\/p>\n

          \n
        • As Shaving mirror.<\/li>\n
        • As Reflectors in automobile headlights & torches.<\/li>\n
        • By dentists to see large images of the teeth of patients.<\/li>\n
        • To produce heat in solar furnaces.<\/li>\n<\/ul>\n

          \"Samacheer<\/p>\n

          Question 6.
          \nWhat are the characteristics of the image formed on a plane mirror?
          \nAnswer:<\/p>\n

            \n
          • Image is upright.<\/li>\n
          • Size of the image is the same as the size of the object.<\/li>\n<\/ul>\n

            Question 7.
            \nState the laws of reflection of light.
            \nAnswer:<\/p>\n

              \n
            • The incident ray, the normal at the point of incidence and the reflected ray, all lie in the same plane.<\/li>\n
            • Angle of incidence is equal to the angle of reflection.<\/li>\n<\/ul>\n

              Question 8.
              \nDescribe the nature of images formed by plane mirrors.
              \nAnswer:<\/p>\n

                \n
              • It is always virtual and erect.<\/li>\n
              • Its size is equal to that of the object<\/li>\n
              • It is formed at the same distance behind the mirror as the object is in front of the mirror.<\/li>\n
              • It is laterally inverted.<\/li>\n<\/ul>\n

                \"Samacheer<\/p>\n

                Question 9.
                \nWhat is lateral inversion in a plane mirror?
                \nAnswer:
                \nIt means the apparent reversal of left and right in the mirror image compared with the object.<\/p>\n

                Question 10.
                \nExplain why a ray of light passing through the centre of curvature of a concave mirror, gets reflected along with the same pattern.
                \nAnswer:
                \nThe ray passing through the centre of curvature incident to the mirror along its normal so < i = < r = 0
                \n\u2234 The ray retraces its pattern<\/p>\n

                Question 11.
                \nHow tall does a mirror have to be to fit an entire person’s body?
                \nAnswer:
                \nThe height of the mirror should behalf of the person’s height regardless of the distance of the person from the mirror.<\/p>\n

                Question 12.
                \nWhat is concave and convex mirror?
                \nAnswer:<\/p>\n

                  \n
                • If the reflecting surface is curved inwards that is called concave mirror.<\/li>\n
                • The reflecting surface is curved outwards, then it is called convex mirror.<\/li>\n<\/ul>\n

                  \"Samacheer<\/p>\n

                  Question 13.
                  \nDefine principal focus of concave mirror.
                  \nAnswer:
                  \nPrincipal focus (F): The point on the principal axis of the spherical mirror where the rays of light parallel to the principal axis meet or appear to meet after reflection from the spherical mirror.<\/p>\n

                  Question 14.
                  \nWhat is focal length (f) of a mirror?
                  \nAnswer:
                  \nThe distance between the pole (P) and the principal focus (F) of the spherical mirror is called the focal length.
                  \nf = \\(\\frac { R }{ 2 }\\) , where R is the radius of curvature of the mirror.<\/p>\n

                  Question 15.
                  \nDefine Radius of curvature.
                  \nAnswer:
                  \nThe radius of the hollow sphere of which the spherical mirror forms a part is called the radius of curvature (R)
                  \nR = 2 \u00d7 focal length<\/p>\n

                  \"Samacheer<\/p>\n

                  Question 16.
                  \nWhat is \u201caperture\u201d?
                  \nAnswer:
                  \nThe diameter of the circular rim of the mirror is called the aperture of the mirror. It is the entire area of the reflecting surface of the mirror.<\/p>\n

                  Question 17.
                  \nDistinguish between real & virtual image.
                  \nAnswer:
                  \nReal :<\/p>\n

                    \n
                  1. Light rays that come from an object actually meet after reflection.<\/li>\n
                  2. It can be obtained on a screen<\/li>\n
                  3. Image is inverted<\/li>\n<\/ol>\n

                    Virtual :<\/p>\n

                      \n
                    1. Light comes from an object does not actually meet but appears to meet.<\/li>\n
                    2. It cannot be obtained on the screen.<\/li>\n
                    3. The image is erect.<\/li>\n<\/ol>\n

                      \"Samacheer<\/p>\n

                      Question 18.
                      \nWhat do you mean by linear magnification?
                      \nAnswer:
                      \nIt is defined as the ratio of the height of the image (hi<\/sub>) to the height of the object (ho<\/sub>).
                      \n\\(m=\\frac{h_{i}}{h_{o}}(\\text { or }) \\quad m=-\\frac{v}{u}\\)<\/p>\n

                      Question 19.
                      \nWhich kind of mirrors are used in the shaving mirror? Why?
                      \nAnswer:
                      \nCancave mirror, to get magnified image. When a cancave mirror is held near the face (between the pole and focus of the mirror) then an upright and magnified image is seen.<\/p>\n

                      Question 20.
                      \nWhich mirror is used as a reflector? Why?
                      \nAnswer:<\/p>\n

                        \n
                      • Concave mirrors are used as reflectors in torches, vehicle headlights and searchlights.<\/li>\n
                      • To get a powerful parallel beam of light.<\/li>\n<\/ul>\n

                        Question 21.
                        \nWrite the uses of cancave mirror
                        \nAnswer:<\/p>\n

                          \n
                        1. As a shaving mirror: Magnified face will be seen<\/li>\n
                        2. As a dentist head mirror: Focuses the lights on to see a small area of the body (teeth, throat, etc.)<\/li>\n
                        3. As reflectors: To get a powerful beam of light<\/li>\n
                        4. In solar heaters: To focus sun light for heaters<\/li>\n<\/ol>\n

                          Question 22.
                          \nWhat do you observe when an object is placed anywhere between P and infinity in front of a convex mirror?
                          \nAnswer:<\/p>\n

                            \n
                          • The image is formed behind the mirror between the pole (P) and focus (F).<\/li>\n
                          • Virtual and erect image.<\/li>\n
                          • Diminished image.<\/li>\n<\/ul>\n

                            \"Samacheer<\/p>\n

                            Question 23.
                            \nWhat is the nature of the image formed by a concave mirror if the magnification produced by the mirror is +4?
                            \nAnswer:
                            \nPositive sign of magnification indicates that image is virtual, erect and enlarged.<\/p>\n

                            Question 24.
                            \nBetween which two points of a concave mirror should an object be placed to obtain a magnification of -2?
                            \nAnswer:
                            \nNegative sign of magnification indicates that image is real and inverted. Sign of image is magnified (enlarge)
                            \n\u2234 Object is placed between F and C.<\/p>\n

                            Question 25.
                            \nTo obtain an image twice the size of the object, between which two points related to a concave mirror should an object be placed?
                            \nAnswer:
                            \nBetween F (principal focus) and C centre of curvature.
                            \nReal Image.<\/p>\n

                            Question 26.
                            \nDraw a ray diagram and also state the position the relative size and nature of image formed by a concave mirror, when an object is placed at C.
                            \nAnswer:
                            \nImage Position: At C, itself
                            \nSize: Same size
                            \nNature : (i) Real
                            \n(ii) Inverted
                            \n\"Samacheer<\/p>\n

                            \"Samacheer<\/p>\n

                            Question 27.
                            \nWhy a pencil partly immersed in water appears to be bent at the water surface.
                            \nAnswer:
                            \nThe pencil dipped in water appears bent due to the refraction of light.
                            \nThe angle of refraction depends on the refractive index of the medium.<\/p>\n

                            Question 28.
                            \nHow should a ray of light be incident on a rectangular glass slab so that it comes out from the opposite side of the slab without being displaced?
                            \nAnswer:
                            \nAlong the normal to the surface or at an angle of incidence of i = 0.<\/p>\n

                            Question 29.
                            \nWhy a convex mirror is preferred for rearview mirrors in cars?
                            \nAnswer:<\/p>\n

                              \n
                            • It always forms virtual, erect, and diminished images.<\/li>\n
                            • The field of view increases.<\/li>\n<\/ul>\n

                              Question 30.
                              \nList four properties of the image formed by a convex mirror.
                              \nAnswer:<\/p>\n

                                \n
                              • Always formed behind the mirror between P & F.<\/li>\n
                              • Virtual & erect<\/li>\n
                              • Size is always smaller than the object.<\/li>\n
                              • Magnification is always positive.<\/li>\n<\/ul>\n

                                \"Samacheer<\/p>\n

                                Question 31.
                                \nList four properties of the image formed by the concave mirror when the object is placed between F & P
                                \nAnswer:<\/p>\n

                                  \n
                                • The image formed behind the mirror<\/li>\n
                                • Enlarged<\/li>\n
                                • Virtual<\/li>\n
                                • Erect<\/li>\n<\/ul>\n

                                  Question 32.
                                  \nWhat is meant by the refraction of light?
                                  \nAnswer:
                                  \nLight does not travel in the same direction in all media. It changes its direction, the bending of a light ray when it passes from one medium to another is called refraction of light.<\/p>\n

                                  Question 33.
                                  \nState the laws of refraction of light.
                                  \nAnswer:
                                  \n(i) The incident ray, the refracted ray, and the normal to the interface of two transparent media at the point of incidence, all lie in the same plane.<\/p>\n

                                  (ii) The ratio of the sine of the angle of incidence to the sine of the angle of refraction is a constant for a light of a given colour and for the given pair of media. This law is also known as Snell\u2019s law of refraction.
                                  \nIf i is the angle of incidence and r is the angle of refraction, then \\(\\frac{\\sin i}{\\sin r}[latex] = constant
                                  \nThis constant is called the refractive index of the second medium with respect to the first medium. T<\/p>\n

                                  \"Samacheer<\/p>\n

                                  Question 34.
                                  \nDefine refractive index & write its unit.
                                  \nAnswer:
                                  \nThe refractive index of the second medium with respect to the first medium is defined as the ratio of the sine of the angle of incidence in the first medium to the sine of the angle of refraction in the second medium.
                                  \nUnit: The refractive index has no unit as it is the ratio of two similar quantities<\/p>\n

                                  Question 35.
                                  \nDefine refractive index in terms of speed of light.
                                  \nAnswer:
                                  \nThe refractive index of a medium is also defined in terms of speed of light in different media
                                  \n\"Samacheer<\/p>\n

                                  Question 36.
                                  \nWhat is total internal reflection?
                                  \nAnswer:
                                  \nTotal internal reflection: When the angle of incidence exceeds the value of the critical angle, the refracted ray is not possible, since r > 90\u00b0, the ray is totally reflected back to the same medium (denser medium). This is called as total internal reflection.<\/p>\n

                                  \"Samacheer<\/p>\n

                                  Question 37.
                                  \nDefine the critical angle.
                                  \nAnswer:
                                  \nThe angle of incidence at which the angle of refraction is 90\u00b0 is called the critical angle.<\/p>\n

                                  Question 38.
                                  \nWhat are the conditions to achieve total internal reflection?
                                  \nAnswer:<\/p>\n

                                    \n
                                  • Light must travel from denser medium (Water) to rarer medium (Air).<\/li>\n
                                  • The angle of incidence inside the denser medium must be greater than that of the critical angle.<\/li>\n<\/ul>\n

                                    Question 39.
                                    \nWhat is mirage? How it occurs?
                                    \nAnswer:<\/p>\n

                                      \n
                                    • Mirage is an optical illusion caused by the refraction of light from the sky by heated air.<\/li>\n
                                    • The air near the ground becomes hotter than the air at higher levels.<\/li>\n
                                    • The refractive index of air increases with its density. Hotter air is less dense, and has smaller refractive index than cooler air.<\/li>\n
                                    • If the air currents are small, that is, the air is still, the optical density of different layers of air increases with height.<\/li>\n
                                    • As a result, light from an object such as a car passes through a medium whose refractive index decreases towards the ground.<\/li>\n
                                    • Thus, a ray of light from such an object successively bends away from the normal and undergoes total internal reflection, if the angle of incidence for the air near the ground exceeds the critical angle.<\/li>\n<\/ul>\n

                                      \"Samacheer<\/p>\n

                                      Question 40.
                                      \nHow do twinkling stars occur? (or) what is the cause of the twinkling of stars?
                                      \nAnswer:
                                      \nRefraction of light:<\/p>\n

                                        \n
                                      • Light from a star is refracted as it passes through our atmosphere because the light
                                        \npasses rapidly through moving cells of air with different densities, temperatures, etc.<\/li>\n
                                      • These cells bend light by different amounts and make the apparent position of the star move around. This movement is seen as twinkling.<\/li>\n<\/ul>\n

                                        Question 41.
                                        \nWhat is the phenomenon used in optical fibre? Explain.
                                        \nAnswer:<\/p>\n

                                          \n
                                        • Optical fibres are extensively used for transmitting audio and video signals through long distances.<\/li>\n
                                        • Optical fibres too make use of the phenomenon of total internal reflection.<\/li>\n
                                        • Optical fibers are fabricated with high-quality composite glass\/quartz fibres.
                                          \nEach fibres consists of a core and cladding. The refractive index of the material of the core is higher than that of the cladding.<\/li>\n<\/ul>\n

                                          When a signal in the form of light is directed at one end of the fibre at a suitable angle, it undergoes repeated total internal reflection along the length of the fibre and finally comes out at the other end. Optical fibres are extensively used for transmitting and receiving electrical signals which are converted to light between the ends of the fibre, over long distances.<\/p>\n

                                          \"Samacheer<\/p>\n

                                          Question 42.
                                          \nWrite any two uses of total internal reflection.
                                          \nAnswer:<\/p>\n

                                            \n
                                          1. Spectacular brilliance of diamonds.<\/li>\n
                                          2. Transmission of audio and video signals to long-distance through optical fibres.<\/li>\n<\/ol>\n

                                            Question 43.
                                            \nWhat are the examples of total internal reflection in nature?
                                            \nAnswer:<\/p>\n

                                              \n
                                            1. Mirage<\/li>\n
                                            2. Twinkling of stars<\/li>\n<\/ol>\n

                                              Question 44.
                                              \nGive two examples of the transparent medium that are denser than air.
                                              \nAnswer:
                                              \nWater, glass.<\/p>\n

                                              Question 45.
                                              \nA coin in a glass beaker appears to rise as the beaker is slowly filled with water why?
                                              \nAnswer:
                                              \nRefraction of light at the air-water interface.<\/p>\n

                                              \"Samacheer<\/p>\n

                                              Question 46.
                                              \nName the spherical mirror(s) that has\/have
                                              \n(i) Virtual principal focus
                                              \n(ii) Real principal focus
                                              \nAnswer:
                                              \n(i) Convex
                                              \n(ii) Concave.<\/p>\n

                                              VII. Long Answers<\/span><\/p>\n

                                              Question 1.
                                              \nList the sign conventions for reflection of light by spherical mirrors.
                                              \n(i) Write the formula for the spherical mirror.
                                              \n(ii) Mirror Equation
                                              \nAnswer:
                                              \n\"Samacheer
                                              \n(i)<\/p>\n

                                                \n
                                              • The object is always placed on the left side of the mirror.<\/li>\n
                                              • All distances are measured from the pole of the mirror.<\/li>\n
                                              • Distances measured in the direction of light are taken as positive (along + X-axis) and those measured in the opposite direction are taken as negative (along – X-axis).<\/li>\n
                                              • All distances measured perpendicular to and above the principal axis (along + Y-axis) are considered to be positive.<\/li>\n
                                              • All distances measured perpendicular to and below the principal axis (along – Y-axis) are considered to be negative. Cartesian sign conventions are used to derive mirror formula and do simple calculations.<\/li>\n<\/ul>\n

                                                \"Samacheer<\/p>\n

                                                (ii) Mirror Equation
                                                \nThe expression relating the distance of the object u, a distance of image v, and focal length f of a spherical mirror is called the mirror equation.
                                                \n[latex]\\frac{1}{f}=\\frac{1}{u}+\\frac{1}{v}\\)<\/p>\n

                                                f – focal length of a spherical mirror
                                                \nu – Distance of the object
                                                \nv – Distance of the image<\/p>\n

                                                Linear Magnification:<\/p>\n

                                                It can be defined as the ratio of the height of the image (hi<\/sub>) to the height of the object (ho<\/sub>)
                                                \nm = \\(\\frac{h_{i}}{h_{o}}(\\text { or }) \\frac{-v}{u}\\)
                                                \nhi<\/sub> = height of the image
                                                \nho<\/sub> = height of the object<\/p>\n

                                                Question 2.
                                                \nState the type of mirror used as
                                                \n(i) Convex mirror
                                                \n(ii) Concave mirror
                                                \nAnswer:
                                                \n(i) Convex mirror :<\/p>\n

                                                  \n
                                                • It gives a wide field of view<\/li>\n
                                                • It produces erect and small size image of the object. [As the vehicles approach the driver from behind, the size of the image increases. When vehicles are moving away from the driver, the image size decreases]<\/li>\n<\/ul>\n

                                                  (ii) Concave mirror:
                                                  \nTo see a large size image of the face.
                                                  \nWhen the object lies in between pole and principal focus, it forms a virtual, erect and enlarged image.<\/p>\n

                                                  \"Samacheer<\/p>\n

                                                  Question 3.
                                                  \nWrite the rules for the construction of image by Concave mirrors, along with ray diagram. .
                                                  \nAnswer:
                                                  \n(i) Rule 1 : A ray passing through the centre of curvature is reflected back along its own path.
                                                  \n\"Samacheer<\/p>\n

                                                  (ii) Rule 2 : A ray parallel to the principal axis passes through the focus after reflection.
                                                  \n\"Samacheer<\/p>\n

                                                  (iii) Rule 3 :A ray passing through the focus gets reflected and travels parallel to the principal axis.
                                                  \n\"Samacheer<\/p>\n

                                                  (iv) Rule 4 : A ray AP incident at the pole of the mirror gets reflected along a path PB
                                                  \nsuch that the angle of incidence APC is equal to the angle of reflection BPC.
                                                  \n\"Samacheer<\/p>\n

                                                  \"Samacheer<\/p>\n

                                                  Question 4.
                                                  \nDescribe the nature and location of the images for the different positions of object which is placed in front of the concave mirror.
                                                  \nAnswer:
                                                  \n\"Samacheer
                                                  \n\"Samacheer<\/p>\n

                                                  VIII. Higher-Order Thinking Skills :<\/span><\/p>\n

                                                  Question 1.
                                                  \nM = 2.42 for diamond. What is the meaning of this statement in relation to the speed of light?
                                                  \nAnswer:
                                                  \nIt means that light travels 2.42 times faster in a vacuum than in a diamond.<\/p>\n

                                                  Question 2.
                                                  \nA convex mirror is in water. What should be the change in its focal length?
                                                  \nAnswer:
                                                  \nNo change. The focal length of a convex mirror does not depend on the nature of the medium.<\/p>\n

                                                  \"Samacheer<\/p>\n

                                                  Question 3.
                                                  \nAre the laws of reflection true in the case of irregular reflection?
                                                  \nAnswer:
                                                  \nYes, at the point of incidence both laws of reflection will hold good.<\/p>\n","protected":false},"excerpt":{"rendered":"

                                                  Tamilnadu State Board New Syllabus Samacheer Kalvi 9th Science Guide Pdf Chapter 6 Light Text Book Back Questions and Answers, Notes. Tamilnadu Samacheer Kalvi 9th Science Solutions Chapter 6 Light 9th Science Guide Light Text Book Back Questions and Answers I. Choose the correct answer : Question 1. A ray of light passes from one …<\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":false,"jetpack_social_options":{"image_generator_settings":{"template":"highway","enabled":false},"version":2}},"categories":[3],"tags":[],"class_list":["post-22763","post","type-post","status-publish","format-standard","hentry","category-class-9"],"jetpack_publicize_connections":[],"jetpack_sharing_enabled":true,"jetpack_featured_media_url":"","_links":{"self":[{"href":"https:\/\/samacheerkalvi.guide\/wp-json\/wp\/v2\/posts\/22763"}],"collection":[{"href":"https:\/\/samacheerkalvi.guide\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/samacheerkalvi.guide\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/samacheerkalvi.guide\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/samacheerkalvi.guide\/wp-json\/wp\/v2\/comments?post=22763"}],"version-history":[{"count":1,"href":"https:\/\/samacheerkalvi.guide\/wp-json\/wp\/v2\/posts\/22763\/revisions"}],"predecessor-version":[{"id":41178,"href":"https:\/\/samacheerkalvi.guide\/wp-json\/wp\/v2\/posts\/22763\/revisions\/41178"}],"wp:attachment":[{"href":"https:\/\/samacheerkalvi.guide\/wp-json\/wp\/v2\/media?parent=22763"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/samacheerkalvi.guide\/wp-json\/wp\/v2\/categories?post=22763"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/samacheerkalvi.guide\/wp-json\/wp\/v2\/tags?post=22763"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}