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## Tamilnadu Samacheer Kalvi 10th Science Solutions Chapter 6 Nuclear Physics

### Samacheer Kalvi 10th Science Nuclear Physics Text Book Back Questions and Answers

Question 1.
(d) (a) and (c)

Question 2.
(a) roentgen
(b) curie
(c) becquerel
(d) all the above.
(d) all the above.

Question 3.
(a) Becquerel
(b) Irene Curie
(c) Roentgen
(d) Neils Bohr
(b) Irene Curie

Question 4.
In which of the following, no change in mass number of the daughter nuclei takes place _____.
(i) α decay
(ii) β decay
(iii) γ decay
(iv) neutron decay
(a) (i) is correct
(b) (ii) and (iii) are correct
(c) (i) & (iv) are correct
(d) (ii) & (iv) are correct.
(b) (ii) and (iii) are correct

Question 5.
……. isotope is used for the treatment of cancer.

Question 6.
Gaming radiations are dangerous because of _____.
(a) it affects eyes & bones
(b) it affects tissues
(c) it produces genetic disorder
(d) it produces an enormous amount of heat.
(c) it produces genetic disorder

Question 7.
……… aprons are used to protect us from gamma radiations.
(b) Iron
(d) Aluminium

Question 8.
Which of the following statements is/are correct?
(i) a particles are photons.
(ii) Penetrating power of γ radiation is very low.
(iii) Ionization power is maximum for a rays.
(iv) Penetrating power of γ radiation is very high.
(a) (i) & (ii) are correct
(b) (ii) & (iii) are correct
(c) (iv) only correct
(d) (iii) & (iv) are correct
(d) (iii) & (iv) are correct

Question 9.
Proton-Proton chain reaction is an example of _____.
(a) Nuclear fission
(b) α – decay
(c) Nuclear fusion
(d) β – decay.
(c) Nuclear fusion

Question 10.
In the nuclear reaction the value of A and Z.
(a) 8, 6
(b) 8, 4
(c) 4, 8
(d) cannot be determined with the given data
(b) 8, 4

Question 11.
Kamini reactor is located at:
(a) Kalpakkam
(b) Koodankulam
(c) Mumbai
(d) Rajasthan
(a) Kalpakkam

Question 12.
Which of the following is/are correct?
(i) Chain reaction takes place in a nuclear reactor and an atomic bomb.
(ii) The chain reaction in a nuclear reactor is controlled
(iii) The chain reaction in a nuclear reactor is not controlled
(iv) No chain reaction takes place in an atom bomb
(a) (i) only correct
(b) (i) & (ii) are correct
(c) (iv) only correct
(d) (iii) & (iv) are correct.
(b) (i) & (ii) are correct

II. Fill in the blanks.

1. One roentgen is equal to ………… disintegrations per second.
2. Positron is an …………
3. Aneamia can be cured by ………… isotope.
4. Abbreviation of ICRP …………..
5. ………… is used to measure exposure rate of radiation in humans.
6. ………. has the greatest penetration power.
7. ZYAZ+1YA + X; Then, X is …………..
8. ZXAZYA This reaction is possible in …………. decay.
9. The average energy released in each fusion reaction is about …………. J.
10. Nuclear fusion is possible only at an extremely high temperature of the order of ……….. K.
11. The radio isotope of …………. helps to increase the productivity of crops.
12. If the radiation exposure is 100 R, it may cause ………….
1. 1.6 × 1015 disintegrations / second
2. antiparticle [1e0]
4. International Commission on Radiological Protection
5. Dosimeter
6. Gama rays
7. X is -1e0
8. gamma
9. 3.84 × 1012 J
10. 107 to 109 K
11. Radio phosphorus P – 32
12. fatal diseases like leukemia.

III. State whether the following statements are true or false: If false, correct the statement.

1. Plutonium -239 is a fissionable material.
2. Elements having atomic number greater than 83 can undergo nuclear fusion.
3. Nuclear fusion is more dangerous than nuclear fission.
4. Natural uranium U-238 is the core fuel used in a nuclear reactor.
5. If a moderator is not present, then a nuclear reactor will behave as an atom bomb.
6. During one nuclear fission on an average, 2 to 3 neutrons are produced.
7. Einstein’s theory of mass energy equivalence is used in nuclear fission and fusion.
1. True
2. False – Elements having atomic number greater than 83 can undergo nuclear fission.
3. True
4. False – Natural U – 238 not used as fuel in a nuclear reactor.
5. True
6. True
7. True

IV. Match the following.

Question 1.
Match the column I with column II.

(a) – (iii)
(b) – (i)
(c) – (iv)
(d) – (ii)

Question 2.
Match the column I with column II.

(a) – (iv)
(b) – (ii)
(c) – (iii)
(d) – (i)

Question 3.
Match the column I with column II.

(a) – (ii)
(b) – (iv)
(c) – (i)
(d) – (iii)

Question 4.
Match the column I with column II.

(a) – (iv)
(b) – (iii)
(c) – (ii)
(d) – (i)

Question 5.
Match the column I with column II.

(a) – (iii)
(b) – (iv)
(c) – (ii)
(d) – (i)

V. Arrange the following in the correct sequence.

Question 1.
Arrange in descending order, on the basis of their penetration power. Alpha rays, beta rays, gamma rays, cosmic rays
gamma rays < beta rays < alpha rays < cosmic rays.

Question 2.
Arrange the following in the chronological order of discovery.

VI. Use the analogy to fill in the blank.

1. Spontaneous process : Natural Radioactivity, Induced process : ………..
2. Nuclear Fusion : Extreme temperature, Nuclear Fission : ………..
3. Increasing crops : Radio phosphorous, Effective functioning of heart : …………
4. Deflected by electric field : a ray, No Deflection : ………….

2. higher temperature
4. γ-ray

VII. Numerical problems.

Question 1.
88Ra226 experiences three a – decay. Find the number of neutrons in the daughter element.
Mass number of 88Ra226 is 266
Atomic number of 88Ra226 is 88
Mass number of α = 4
Atomic number of α = 2
After 3 a decay
Mass number of the daughter element is
= 266 – (3 × 4)
= 266 – 12
= 254
Atomic number of the daughter element is
= 88 – (3 × 2)
= 88 – 6
= 82
Number of neutrons is
= 254 – 82
= 172

Question 2.
A cobalt specimen emits induced radiation of 75.6 millicurie per second. Convert this disintegration in to becquerel (one curie = 3.7 × 1010 Bq).
1 curie = 3.7 × 1010 Bq
∴ 75.6 × 10-3 curie = 75.6 × 10-3 × 3.7 × 1010
= 279.72 × 107 Bq
= 279.72 × 107 Becquerel

VIII. Assertion and reason type questions.

Question 1.
Assertion: A neutron impinging on U235, splits it to produce Barium and Krypton.
Reason: U – 235 is a fissile material.
(a) If both the assertion and the reason are true and the reason is the correct explanation of the assertion.
(b) If both the assertion and the reason are true, but the reason is not the correct explanation of the assertion.
(c) If the assertion is true, but the reason is false.
(d) If the assertion is false, but the reason is true.
(a) If both the assertion and the reason are true and the reason is the correct explanation of the assertion.

Question 2.
Assertion: In a 3 – decay, the neutron number decreases by one.
Reason: In 3 – decay atomic number increases by one.
(a) If both the assertion and the reason are true and the reason is the correct explanation of the assertion.
(b) If both the assertion and the reason are true, but the reason is not the correct explanation of the assertion.
(c) If the assertion is true, but the reason is false.
(d) If the assertion is false, but the reason is true.
(a) If both the assertion and the reason are true and the reason is the correct explanation of the assertion.

Question 3.
Assertion: Extreme temperature is necessary to execute nuclear fusion.
Reason: In a nuclear fusion, the nuclei of the reactants combine releasing high energy.
(a) If both the assertion and the reason are true and the reason is the correct explanation of the assertion.
(b) If both the assertion and the reason are true, but the reason is not the correct explanation of the assertion.
(c) If the assertion is true, but the reason is false.
(d) If the assertion is false, but the reason is true.
(b) If both the assertion and the reason are true, but the reason is not the correct explanation of the assertion.

Question 4.
Assertion: Control rods are known as ‘neutron seeking rods’.
Reason: Control rods are used to perform sustained nuclear fission reaction.
(a) If both the assertion and the reason are true and the reason is the correct explanation of the assertion.
(b) If both the assertion and the reason are true, but the reason is not the correct explanation of the assertion.
(c) If the assertion is true, but the reason is false.
(d) If the assertion is false, but the reason is true.
(a) If both the assertion and the reason are true and the reason is the correct explanation of the assertion.

IX. Answer in one or two words (VSA).

Question 1.
Henri Becquerel

Question 2.
Which radioactive material is present in the ore of pitchblende?
Uranium is the radioactive material is present in the ore of pitchblende.

Question 3.
Write any two elements which are used for inducing radioactivity?
Boron and aluminium

Question 4.
Write the name of the electromagnetic radiation which is emitted during natural radioactivity.
Gamma rays are the electromagnetic radiation which is emitted during natural radioactivity.

Question 5.
If A is a radioactive element which emits an α – particle and produces 104Rf259. Write the atomic number and mass number of the element A.

Mass number A = 259 + 4 = 263
Atomic number Z = 104 + 2 = 106

Question 6.
What is the average energy released from a single fission process?
200 MeV

Question 7.
Which hazardous radiation is the cause for the genetic disease?
γ – ray (Gamma-ray) or any high energy nuclear particle passes through a human being, it disrupts the entire normal functioning of the biological system and the effect may be an either pathological or genetic disease.

Question 8.
What is the amount of radiation that may cause death of a person when exposed to it?
600 R.

Question 9.
When and where was the first nuclear reactor built?
The first nuclear reactor was built in 1942 at Chicago, USA.

Question 10.
Give the SI unit of radioactivity.
The SI unit of radioactivity is becquerel.

Question 11.
Which material protects us from radiation?

X. Answer the following questions in a few sentences.

Question 1.
Write any three features of natural and artificial radioactivity.

Question 2.
Define critical mass.
The minimum mass of fissile material necessary to sustain the chain reaction is called ‘critical mass (mc)’. It depends on the nature, density and the size of the fissile material.

Question 3.
Define one roentgen.
One roentgen is defined as the quantity of radioactive substance which produces a charge of 2.58 × 10-4 coulomb in 1 kg of air under standard conditions of pressure, temperature and humidity.

Question 4.
State Soddy and Fajan’s displacement law.
(i) When a radioactive element emits an alpha particle, a daughter nucleus is formed whose mass number is less by 4 units and the atomic number is less by 2 units, than the mass number and atomic number of the parent nucleus.

(ii) When a radioactive element emits a beta particle, a daughter nucleus is formed whose mass number is the same and the atomic number is more by 1 unit, than the atomic number of the parent nucleus.

Question 5.
Give the function of control rods in a nuclear reactor.
Control rods are used to control the number of neutrons in order to have a sustained chain reaction. Mostly boron or cadmium rods are used as control rods. They absorb the neutrons.

Question 6.
In Japan, some of the newborn children are having congenital diseases. Why?
In Japan, there was a leakage of nuclear radiations in some areas. In those areas, if the new born children handled with careless they are exposed to harmful radiations then they have congenital diseases.

Question 7.
Mr. Ramu is working as an X – ray technician in a hospital. But, he does not wear the lead aprons. What suggestion will you give to Mr. Ramu?
The intensity of X-rays is very low. So, X-rays do not produce any severe effects. There are certains clothes that can be used while operating X-ray machines. Ramu can use them and so he may not be severely affected by X-rays, he should avoid eating and drinking when he is working with X-rays.

Question 8.
What is stellar energy?
Fusion reaction that takes place in the cores of the Sun and other stars results in an enormous amount of energy, which is called stellar energy.

Question 9.
Give any two uses of radio isotopes in the field of agriculture?
The radio isotope of phosphorous (P-32) helps to increase the productivity of crops. The radiations from the radio isotopes can be used to kill the insects and parasites and prevent the wastage of agricultural products.

Question 10.
What is stellar energy?
Fusion reaction that takes place in the cores of the Sun and other stars results in an enormous amount of energy, which is called as stellar energy.

XI. Answer the following questions in detail.

Question 1.
Explain the process of controlled and uncontrolled chain reactions.
(i) Controlled chain reaction: In the controlled chain reaction the number of neutrons released is maintained to be one. This is achieved by absorbing the extra neutrons with a neutron absorber leaving only one neutron to produce further fission. Thus, the reaction is sustained in a controlled manner. The energy released due to a controlled chain reaction can be utilized for constructive purposes. Controlled chain reaction is used in a nuclear reactor to produce energy in a sustained and controlled manner.

(ii) Uncontrolled chain reaction: In the uncontrolled chain reaction the number of neutrons multiplies indefinitely and causes fission in a large amount of the fissile material. This results in the release of a huge amount of energy within a fraction of a second. This kind of chain reaction is used in the atom bomb to produce an explosion.

Question 2.
Compare the properties of alpha, beta and gamma radiations.

Question 3.
What is a nuclear reactor? Explain its essential parts with their functions.
A Nuclear reactor is a device in which the nuclear fission reaction takes place in a self-sustained and controlled manner to produce electricity.
Components of a nuclear reactors:
The essential components of a nuclear reactor are

1. fuel,
2. moderator,
3. control rod,
4. coolant and
5. protection wall.

1. Fuel : A fissile material is used as the fuel. The commonly used fuel material is uranium.
2. Moderator : A moderator is used to slow down the high energy neutrons to provide slow neutrons. Graphite and heavy water are the commonly used moderators
3. Control rod : Control rods are used to control the number of neutrons in order to have sustained chain reaction. Mostly boron or cadmium rods are used as control rods. They absorb the neutrons.
4. Coolant : A coolant is used to remove the heat produced in die reactor core, to produce steam. This steam is used to run a turbine in order to produce electricity. Water, air and helium are some of the coolants.
5. Protection wall : A thick concrete lead wall is built around the nuclear reactor in order to prevent the harmful radiations from escaping into the environment.

XII. HOT Questions.

Question 1.
The mass number of a radioactive element is 232 and its atomic number is 90. When this element undergoes certain nuclear reactions, it transforms into an isotope of lead with a mass number 208 and an atomic number 82. Determine the number of alpha and beta decay that can occur.
$$_{90} \mathrm{x}^{232} \stackrel{4 \beta}{\longrightarrow} 94^{\mathrm{Y}^{232}+4_{-4} \mathrm{e}^{\circ}}$$ (4β decay)
From the result of β decay,
$$94^{232} \stackrel{6 \alpha}{\longrightarrow} 82^{\mathrm{Pb}^{208}+6}_{} \mathrm{He}^{4}$$ (6α decay)
The number of α decay = 6
The number of β decay = 4.

Question 2.
‘X – rays should not be taken often’. Give the reason.
X-rays have some low intensity. Even then if a person undergoes the exposure of X-ray, his skin may be affected. The tissues near by the bones may be damaged.

Question 3.
Cell phone towers should be placed far away from the residential area – why?
From the cell phone towers micro-waves are scattered for a particular area. This may affect small children and aged people. If people are exposed with those rays very often then they may be severly affected.

### Samacheer Kalvi 10th Science Nuclear Physics Additional Important Questions and Answers

Question 1.
The elements that undergo spontaneous radioactivity:
(a) Uranium
(d) None of the above

Question 2.
The artificial (or) induced radioactive element is _____.
(a) Uranium
(b) Boron
(d) none of these.
(b) boron

Question 3.
The nucleons in a nucleus are attracted by:
(a) electrostatic force
(b) gravitational force
(c) nuclear force
(d) magnetic force
(c) nuclear force

Question 4.
In p decay by one.
(a) mass number decreases
(b) atomic number decreases
(c) neutron number decreases
(d) proton number decreases
(c) neutron number decreases

Question 5.
The charge of the α rays _____.
(a) 2e
(b) -e
(c) 0
(d) none of these.
(a) 2e

Question 6.
In which process positron is emitted?
(c) nuclear fission
(d) nuclear fussion

Question 7.
The atomic number of the elements that exhibit natural radioactivity is:
(a) less than 83
(b) more than 83
(c) more than 42
(d) more than 82
(b) more than 83

Question 8.
The ionising power of the α rays _____.
(a) 100 times greater than the β rays
(b) 1000 times greater than the γ rays
(c) very less ionization
(d) both (a) and (b).
(d) both (a) and (b).

Question 9.
In the reaction  is:
(a) 6C13
(b) 6C12
(c) 7N13
(d) 8O16
(b) 6C12

Question 10.
Ionising power of β rays _____.
(а) 100 times greater than α rays
(b) 100 times less than α rays
(c) comparatively very less ionization power
(d) 1000 times less than γ rays.
(b) 100 times less than α rays

Question 11.
During α – decay the mass number of the daughter element is:
(a) more by 2 units
(b) less by 2 units
(c) more by 4 units
(d) less by 4 units
(d) less by 4 units

Question 12.
When α – particle is emitted the atomic number of daughter element is:
(a) more by 4 units
(b) less by 4 units
(c) less by 2 units
(d) more by 2 units
(c) less by 2 units

Question 13.
Which power has more penetrating power?
(a) α rays
(b) γ rays
(c) β rays
(d) X rays.
(b) γ rays

Question 14.
What is the charge of alpha particle?
(a) -e
(b) +e
(c) zero
(d) +2e
(d) +2e

Question 15.
Which of the following has speed from 1/10 to 1/20 times the speed of light?
(a) β
(b) α
(c) γ
(d) all the above
(b) α

Question 16.
In α – decay _____.
(a) atomic number decreases by 2 and the mass number decreases by 4
(b) atomic number increases by 2 and the mass number decrease by 4
(c) there is no change in atomic and mass number
(d) neutron number decreases by one.
(a) atomic number decreases by 2 and the mass number decreases by 4

Question 17.
Which of the following is a fertile material?
(a) Thorium – 232
(b) Uranium – 238
(c) Plutonium – 240
(d) All the above
(d) All the above

Question 18.
If the mass of the fissile material is less than the critical mass, then it is termed as:
(a) supercritical
(b) critical
(c) subcritical
(d) none of the above
(b) critical

Question 19.
1 curie is equal to _____.
(a) the radioactivity of 1 gram of uranium
(b) 1 decay/second
(c) 3.7 × 1010 becquerel
(d) 1.6 × 1012 decay / second.
(c) 3.7 × 1010 becquerel

Question 20.
During nuclear fusion which of the following are emitted:
(a) alpha rays
(b) positrons
(c) neutrons
(d) all the above
(d) all the above

Question 21.
Anaemia can be diagonised by:
(a) 15P32
(b) 26Fe59
(c) 11Na24
(d) 28Fe59
(b) 26Fe59

Question 22.
I – 131 is used in the treatment of _____.
(a) cancer
(b) skin disease
(c) disease in the thyroid gland
(d) tumour.
(c) disease in the thyroid gland

Question 23.
In which decay atomic number of daughter element is increased by 1 unit?
(a) α – decay
(b) β – decay
(c) γ – decay
(d) neutron decay
(b) β – decay

Question 24.
in nuclear fusion ………… is satisfied.
(a) law of conservation of energy
(b) law of conservation of momentum
(c) law of conservation angular momentum
(d) mass energy relation
(d) mass energy relation

Question 25.
(a) 100 R
(b) 600 R
(c) 250 R
(d) 250 mR per week.
(d) 250 mR per week.

Question 26.
Hydrogen bomb is based on the principle of:
(c) nuclear fusion
(d) nuclear fission
(c) nuclear fusion

Question 27.
Uncontrolled chain reaction yields _____.
(a) nuclear reactor
(b) atom bomb
(c) hydrogen bomb
(d) breeder reactor.
(b) atom bomb

Question 28.
In the following reaction.
1H3 + 1H2 → X + Y + energy X and Y are:
(a) 2He3, 0n1
(b) 2He4, 0n1
(c) 1H2, 0n1
(d) 1H3, 0n1
(b) 2He4, 0n1

Question 29.
The number of α and ß particles emitted when 92U238 decays to 82Pb206 are respectively:
(a) 6, 8
(b) 8, 6
(c) 4, 3
(d) 3, 4
(b) 8, 6

Question 30.
The fusion process can be carried out only at a temperature of _____.
(a) 1000°C
(b) 100°C
(c) 104°C
(d) 107 K.
(d) 107 K.

Question 31.
Which of the following is used to cure goiter?
(a) Na24
(b) I131
(c) P32
(d) Fe59
(b) I131

Question 32.
Which radio isotope is used to check the function of heart?
(a) Na24
(b) Fe59
(c) Co60
(d) I131
(a) Na24

Question 33.
The fuel of the prototype fast breeder reactor is _____.
(a) low enriched uranium
(b) carbides of uranium
(c) high enriched uranium
(d) oxides of plutonium and uranium.
(d) oxides of plutonium and uranium.

Question 34.
Which radio isotope is used as a smoke detector?
(a) Cf232
(b) I131
(c) Co60
(d) Am241
(d) Am241

Question 35.
The control rod used in a nuclear reactor is _____.
(a) barium
(b) carbon
(d) Na.

II. Fill in the blanks.

1. Radium was discovered by ………..
2. The photoelectric effect is an instantaneous process Natural radioactivity is a ………..
3. The elements with atomic number ……… undergo spontaneous radioactivity.
4. In natural radioactivity emission of radiation is due to ………. of a nucleus.
5. One disintegration per second is equal to ………..
6. S.I unit of radioactivity is ………….
7. The speed of ………. can go upto 9/10 times the velocity of light.
8. α ray is …………
9. ……….ray consists of photons.
10. ………… and ………… are deflected by electric and magnetic fields.
11. When uranium decays into thorium ……….. particle is emitted.
12. In ………… decay there is no change in the mass number of the product nuclear.
13. The minimum mass of a fissile material necessary to sustain the chain reaction is called …………
14. The value of 1MeV in joules is ………..
15. In the transformation 1H2 + 1H2 → X + energy. X is …………
16. Einstein’s mass energy relation is ………….
17. ……….causes the mutation in the human gene.
18. ……….. is also used in treatment of skin cancer.
19. The safe limit for receiving the radiation is ………….
20. The substances that are used as coolants are ………….. and
21. ………… reactors convert non-fissionable material units.
22. The expansion of BARC is ………….
23. The number of nuclear reactor that are operating in India are ……………
24. Identify X in the following transformation 12Mg24 + 0n1 → X + 1n1. X is ………….
25. In the reaction 92U238 + 0n193NP239 + X. X is ………….
1. Marie Curie and pierre Curie
2. Spontaneous
3. more than 83
4. self-disintegration
5. Becquerel
6. Becquerel
7. β rays
8. a helium nucleus
9. Gamma
10. Alpha, beta
11. alpha
12. beta
13. critical mass
14. 1.602 × 10-13 J
15. 2He4
16. E = mc2
19. 100 mR per week
20. Water, air and helium
21. Breeder
22. Bhaba Atomic Research Centre
23. 22
24. 11Na24
25. -1e0

III. State whether the following statements are true or false: If false, correct the statement.

1. Artificial radioactivity is induced in the elements like boron, aluminum etc.
2. Natural radioactivity can be controlled.
3. 1 Rd = 3.7 × 1010 disintegrations / second.
4. The S.I units of radioactivity is roentgen.
5. The charge of each beta particle is – e
6. Beta ray travels with velocity of light.
7. Example for alpha decay is 92U23890Th234 + 2He4
8. Otto Hann and Strassman discovered nuclear fission.
9. In the mass of the fissile material is more than the critical mass it is termed as supercritical.
10. Hydrogen bomb is based on uncontrolled chain reaction.
11. 1eV = 1.602 × 10-16 Joule.
12. Hydrogen is based on nuclear fusion.
13. Positrons are emitted in nuclear fusion.
14. To diagnose anaemia P32 is used.
15. Radio phosphorous is used in the treatment of skin diseases.
16. To prevent the leakage of nuclear radiation concrete wall with lead lining is used.
1. True
2. False – Artificial radio activity can be controlled.
3. False – 1 curie = 3.7 × 10106 disintegrations / second.
4. False – The S.l unit of radioactivity is Becquerel.
5. True
6. False – Gamma ray travels with velocity of light.
7. True
8. True
9. True
10. False – Atom bomb is based on uncontrolled chain reaction.
11. False – 1eV = 1.602 × 10-9 Joule
12. True
13. True
14. False – To diagonise aneamia Fe59 is used.
15. True
16. True
17. True

IV. Match the following.

Question 1.
Match the Column I with Column II.

(a) – (iii)
(b) – (iv)
(c) – (v)
(d) – (i)

Question 2.
Match the Column I with Column II.

(a) – (iv)
(b) – (v)
(c) – (ii)
(d) – (i)

Question 3.
Match the Column I with Column II.

(a) – (v)
(b) – (iv)
(c) – (i)
(d) – (ii)

V. Numerical problems.

Question 1.
A radioactive isotope emits radiation of 7.4 × 104 G Bq per second. Convert this disintegration in terms of curie.
One curie = 3.7 × 1010 Becquerel
Becquerel (1 Bq) = One disintegration / second
∴ 1 Bq = $$\frac{1}{3.7×10^{10}}$$ curie
∴ 7.4 × 104 G Bq
= 7.4 × 104 × 109 × $$\frac{1}{3.7×10^{10}}$$
= 2 × 103 curie
= 2,000 curie

Question 2.
The isotope 92U238 successfully undergoes three α – decays and two β – decays. What is the resulting isotope?
Number and nature of decays = 3α and 2β
Atomic number of isotope is Z = 92
Mass number of isotope is A = 238
Resulting isotope:
After the emission of 3α particles atomic number
Z’ = Z = (3 × 2)
= Z – 6
= 92 – 6
Z’ = 86
After the emission of 2β particles atomic number
Z” = Z – 2 (-1) = 86 + 2 = 88
Mass number after the emission of 3α particles
A’ = A – 3α
= 238 – 3(4)
= 238 – 12
= 226
Mass number after the emission of 2β particles
A” = A’ – 2(0)
= 226
∴ Resulting isotope is 88Ra226

Question 3.
88Ra226 experiences one α – decay and one β – decay. Calculate the number of neutrons in the final daughter nucleus that is formed.
α particle = 2He4
Atomic number of α particle = 2
Mass number of α particle = 4

Number of neutrons = Mass number – atomic number
= 222 – 87 = 135

Question 4.
State the number of protons, electrons neutrons and nucleons in 4Be9 atom.
Atomic number of 4Be9 atom Z = 4
Mass number of 4Be9 atom A = 9
Number of protons = Atomic number Z = 4
Number of neutrons = A – Z = 9 – 4 = 5
Number of nucleons = A = 9

Question 5.
Determine X and Y in the following transformations.
(i) 4Be9 + α → X
(ii) 92U235 + 0n150Ba141 + Y + 30n1
(i) 4Be9 + 2He46C13 [α = 2He4]
∴ X = 6C13

(ii) 92U235 + 0n150Ba141 + Y + 30n1
Equating atomic number on both sides we get,
235 + 1 = 141 + A + 3
236 = 144 + A
∴ A = 236 – 144
= 92
Equating atomic number on both sides are get
92 + 0 = 56 + 2 + 0
Z = 92 – 56 = 36
∴ Y is 36Kr92

Question 6.
Calculate the amount energy released when a radioactive element undergoes fusion and results in a mass defect of 4g.
Velocity of light = 3 × 108 m/s
Mass defect Δm = 4 × 10-3
By Einstein’s equation, energy released
E = mC²
= (4 × 10-3) × (3 × 108
= 36 × 1013 J
= 3.6 × 1014 J

Question 7.
Identify the radio isotopes in the following reactions.
(i) 15P8 + 0n1 → X + γ
(ii) 0n1ZYA + -1e0 + γ
(i) 15P31 + 0n1 → X + γ
Mass number of X = 31 + 1 = 32
Atomic number of Y= 15 + 0 =15
∴ X is 15P31

(ii) 0n1ZYA + -1e0 + γ
Mass number 1 = A + 0
∴ A = 1
Atomic number 0 = Z – 1
∴ Z = 1
ZYA is 1H1

VI. Assertion and reason type questions.

Question 1.
Assertion: Natural radioactivity is a spontaneous process.
Reason: It cannot be controlled.
(a) If both the assertion and the reason are true and the reason is the correct explanation of the assertion.
(b) If both the assertion and the reason are true, but the reason is not the correct explanation of the assertion.
(c) If the assertion is true, but the reason is false.
(d) If the assertion is false, but the reason is true.
(a) If both the assertion and the reason are true and the reason is the correct explanation of the assertion.

Question 2.
Assertion: In artificial radioactivity neutron and positron are emitted. Reason: It can be controlled.
(a) If both the assertion and the reason are true and the reason is the correct explanation of the assertion.
(b) If both the assertion and the reason are true, but the reason is not the correct explanation of the assertion.
(c) If the assertion is true, but the reason is false.
(d) If the assertion is false, but the reason is true.
(b) If both the assertion and the reason are true, but the reason is not the correct explanation of the assertion.

Question 3.
Assertion: p rays are electrons.
Reason: p rays travel with speed of light.
(a) If both the assertion and the reason are true and the reason is the correct explanation of the assertion.
(b) If both the assertion and the reason are true, but the reason is not the correct explanation of the assertion.
(c) If the assertion is true, but the reason is false.
(d) If the assertion is false, but the reason is true.
(c) If the assertion is true, but the reason is false.

Question 4.
Assertion: Gamma rays have maximum ionising power.
Reason: Alpha rays have low penetrating power.
(a) If both the assertion and the reason are true and the reason is the correct explanation of the assertion.
(b) If both the assertion and the reason are true, but the reason is not the correct explanation of the assertion.
(c) If the assertion is true, but the reason is false.
(d) If the assertion is false, but the reason is true.
(d) If the assertion is false, but the reason is true.

Question 5.
Assertion: Critical mass of a fissile material is the mass necessary to sustain chain reaction.
Reason: Critical mass depends on the nature, density and size of the fissile material.
(a) If both the assertion and the reason are true and the reason is the correct explanation of the assertion.
(b) If both the assertion and the reason are true, but the reason is not the correct explanation of the assertion.
(c) If the assertion is true, but the reason is false.
(d) If the assertion is false, but the reason is true.
(c) If the assertion is true, but the reason is false.

Question 6.
Assertion: Nuclear fusion takes place in the cores of the sun and other stars.
Reason: Nuclear fusion is called as thermonuclear reaction.
(a) If both the assertion and the reason are true and the reason is the correct explanation of the assertion.
(b) If both the assertion and the reason are true, but the reason is not the correct explanation of the assertion.
(c) If the assertion is true, but the reason is false.
(d) If the assertion is false, but the reason is true.
(a) If both the assertion and the reason are true and the reason is the correct explanation of the assertion.

Question 7.
Assertion: An alpha particle carries double the positive charge of protons.
Reason: The charge of alpha particle is equal to charge on the helium nucleus.
(a) If both the assertion and the reason are true and the reason is the correct explanation of the assertion.
(b) If both the assertion and the reason are true, but the reason is not the correct explanation of the assertion.
(c) If the assertion is true, but the reason is false.
(d) If the assertion is false, but the reason is true.
(a) If both the assertion and the reason are true and the reason is the correct explanation of the assertion.

Question 8.
Assertion: Gamma rays are electromagnetic waves.
Reason: Gamma rays travel with speed of light.
(a) If both the assertion and the reason are true and the reason is the correct explanation of the assertion.
(b) If both the assertion and the reason are true, but the reason is not the correct explanation of the assertion.
(c) If the assertion is true, but the reason is false.
(d) If the assertion is false, but the reason is true.
(a) If both the assertion and the reason are true and the reason is the correct explanation of the assertion.

VII. Answer in one or two words (VSA).

Question 1.
Who discovered the nucleus?
Rutherford

Question 2.
This phenomenon of spontaneous emission of radiation from certain elements on their own is called ‘Natural radioactivity’.

Question 3.
State elements exhibiting radioactivity with atomic number less than 83.

Question 4.
What is the nature of radioactive substances?
They are earth metals and transition metals.

Question 5.
Define ‘One Rutherford (Rd)’.
It is another unit of radioactivity. It is defined as the quantity of a radioactive substance, which produces 106 disintegrations in one second.
1 Rd = 106 disintegrations per second.

Question 6.
In 4Be9 + 2He4 → X. What is X?
X is 6C13

Question 7.
What is the value of 1 curie?
1 curie = 3.7 × 1010 disintegrations / second.

Question 8.
State the value of Rutherford.
1 Rutherford = 106 disintegrations / second.

Question 9.
Explain the term ‘fissile material’ Give an example.
Fissionable material is a radioactive element, which undergoes fission in a sustained manner when it absorbs a neutron. It is also termed as ‘fissile material’.
E.g. U235, plutonium (Pu239 and Pu241)

Question 10.
Which ray has greatest ionising power?
Alpha ray

Question 11.
Which ray posses minimum ionising power?
Gamma ray

Question 12.
Which ray is not deflected by electric and magnetic fields?
Gamma ray

Question 13.
Name the ray that travels with speed about 9/10 times that of light?
Beta ray

Question 14.
What is the charge of particle?
It’s charge is +2e.

Question 15.
Which particle has a charge of -e?
Beta particle

Question 16.
State that the ray consisting of protons.
Gamma ray

Question 17.
When uranium emits an alpha particle which element is obtained as daughter element.
Thorium 90Th234

Question 18.
Mention the value of 1eV in terms of joule.
1eV = 1.602 × 10-19 joule

Question 19.
What is the value of 1Mev?
1MeV = 106eV = 1.602 × 10-13 joule

Question 20.
Which radio isotope is used in the treatment of skin diseases?

Question 21.
What is the use of radio iodine?
Radio iodine is used to cure goiter.

Question 22.
Which isotope is used in airlines?
Califorium Cf232 is used in airlines.

Question 23.
State the isotope used as a smoke detector.
Americium Am241

Question 24.
Write down the uses of a nuclear reactor.
Uses of a nuclear reactor

• Nuclear reactors are widely used in power generation.
• They are also used to produce radioisotopes, which are used in a variety of applications
• Some reactors help us to do research in the field of nuclear physics.
• Breeder reactors are used to convert non-fissionable materials into fissionable materials.

Question 25.
What are gamma rays?
Gamma rays are electromagnetic waves consisting of photons.

Question 26.
Who discovered Cathode rays.
J.J. Thomson

VIII. Answer the following question in few sentences.

Question 1.
The phenomenon of nuclear decay of certain elements with the emission of radiations like alpha, beta, and gamma rays is called ‘radioactivity’.

Question 2.
What is meant by natural radioactivity?
This phenomenon of spontaneous emission of radiation from certain elements on their own is called ‘natural radioactivity’.

Question 3.
Define Rutherford.
It is defined as the quantity of a radioactive substance, which produces 106 disintegrations in one second.
1 Rd = 106 disintegrations per second.

Question 4.
What is the unit of radioactivity? Define it.
The SI unit of radioactivity is becquerel. It is defined as the quantity of one disintegration per second.

Question 5.
Define nuclear fission. State an example.
This process of breaking (splitting) up of a heavier nucleus into two smaller nuclei with the release of a large amount of energy and a few neutrons is called ‘nuclear fission’.
Eg: Nuclear fission of a uranium nucleus (U235)
92U235 + 0n156Ba141 + 36Kr92 + 30n1 + Q (energy)

Question 6.
How a product nucleus is identified in a nuclear reaction?
In a nuclear reaction, the element formed as the product nucleus is identified by the atomic number of the resulting nucleus and not by its mass number.

Question 7.
What is fissile material?
A fissionable material is a radioactive element, which undergoes fission in a sustained manner when it absorbs a neutron. It is also termed as ‘fissile material’.
Eg: U235, plutonium (Pu239 and Pu241)

Question 8.
What are fertile materials? Mention examples.
There are some radioactive elements, which can be converted into fissionable material. They are called as fertile materials.
Eg: Uranium – 238, Thorium – 232, Plutonium – 240.

Question 9.
What is the composition of natural uranium?
Natural uranium consists of 99.28 % of 92U238 and 0.72 % of 92U235.

Question 10.
What is nuclear fusion? State an example.
The process in which two lighter nuclei combine to form a heavier nucleus is termed as ‘nuclear fusion’.
Eg: 1H2 + 1H22He4 + Q (Energy)

Question 11.
What is meant by chain reaction?
A chain reaction is a self-propagating process in which the number of neutrons goes on multiplying rapidly almost in a geometrical progression.

Question 12.
What is meant by mass defect?
The mass of the daughter nucleus formed during a nuclear reaction (fission and fusion) is lesser than the sum of the masses of the two parent nuclei. This difference in mass is called mass defect.

Question 13.
Nuclear fusion is named as thermonuclear reaction. Why?
Nuclear fusion is possible only at an extremely high temperature of the order of 107 to 109 K and a high pressure to push the hydrogen nuclei closer to fuse with each other. Hence, it is named as ‘Thermonuclear reaction’.

Question 14.
What are the uses of radio isotopes in industries?

1. An isotope of californium (Cf252) is used in the airlines to detect the explosives in the luggage.
2. An isotope of Americium (Am241) is used in many industries as a smoke detector.

Question 15.
What is the age of Earth?
It is nearly 4.54 × 109 years (around 45 Crore 40 lakh years).

Question 16.
What do you know about dosimeter?
Dosimeter is a device used to detect the levels of exposure of an ionizing radiation.

Question 17.
What is the function of moderator in a nuclear reactor?
A moderator is used to slow down the high energy neutrons to provide slow neutrons. Graphite and heavy water are the commonly used moderators.

Question 18.
How do coolants function in a nuclear reactor?
A coolant is used to remove the heat produced in the reactor core, to produce steam. This steam is used to run a turbine in order to produce electricity. Water, air and helium are some of the coolants.

Question 19.
Name some operating reactors in India.
Cirus, Dhuruva and Pumima.

Question 20.
Define Curie.
Curie is defined as the quantity of a radioactive substance, which undergoes 3.7 × 1010 disintegrations in one second. This is actually close to the activity of 1 g of radium-226.

IX. Answer the following question in detail.

Question 1.
Write short notes on induced radioactivity.

This kind of radioactivity was discovered by Irene Curie and F.Joliot in 1934. Artificial radioactivity is induced in certain lighter elements like boron, aluminium etc., by bombarding them with radiations such as ‘alpha particles’ emitted during the natural radioactivity of uranium. This also results in the emission of invisible radiations and elementary” particles. During such a disintegration, the nucleus which undergoes disintegration is called ‘parent nucleus’ and that which is produced after the disintegration is called a ‘daughter nucleus’. The panicle, which is used to induce the artificial disintegration is termed as projectile and the particle which is produced after the disintegration is termed as ejected panicle. When the projectile hits the parent nucleus, it is converted into an unstable nucleus, which in turn decays spontaneously emitting the daughter nucleus along with an ejected particle.

If you denote the parent and daughter nuclei as X and Y respectively, then the nuclear disintegration is represented as follows: X (P,E) Y. Here, P and E represent the projectile particle and ejected particle respectively.
4Be9 + 2He46C13*
6C13*6C12 + 0n1
In the above nuclear reaction, 6C13* is unstable and is radioactive. This reaction can be represented as 4Be9 (α, n) 4C12
4Be9 + 2He46C12 + 0n1

Question 2.
Explain the concept of ‘Hydrogen bomb’.
Hydrogen Bomb:

• This releases a huge amount of energy in a very small time interval and leads to a Hydrogen bomb is based on the principle of nuclear fusion.
• A hydrogen bomb is always designed to have an inbuilt atom bomb which creates the high temperature and pressure required for fusion when it explodes.
• Fusion takes place in the hydrogen core and leads to the release of a very large amount of energy in an uncontrolled manner.
• The energy released in a hydrogen bomb (or fusion bomb) is much higher than that released in an atom bomb (or fission bomb).

Question 3.
Explain
(i) alpha decay,
(ii) Beta decay,
(iii) gamma decay
(i) Alpha decay : A nuclear reaction in which an unstable parent nucleus emits an alpha particle and forms a stable daughter nucleus, is called, ‘alpha decay’.
Eg: Decay of uranium (U238) to thorium (Th234) with the emission of an alpha particle.
92U23890Th234 + 2He4 (α – decay)
In α – decay, the parent nucleus emits an a particle and so it is clear that for the daughter nucleus, the mass number decreases by four and the atomic number decreases by two.

(ii) Beta decay : A nuclear reaction, in which an unstable parent nucleus emits a beta particle and forms a stable daughter nucleus, is called ‘beta decay’.
Eg: Beta decay of phosphorous.
15P3216S32 + -1e0(β – decay)
In β – decay there is no change in the mass number of the daughter nucleus but the atomic number increases by one. In a nuclear reaction, the element formed as the product nucleus is identified by the atomic number of the resulting nucleus and not by its mass number.

(iii) Gamma decay: In a γ – decay, only the energy level of the nucleus changes. The atomic number and mass number of the radioactive nucleus remain the same.

Question 4.
What is the principle of atom bomb? Describe its structure.
The atom bomb is based on the principle of uncontrolled chain reaction. In an uncontrolled chain reaction, the number of neutrons and the number of fission reactions multiply almost in a geometrical progression. This releases a huge amount of energy in a very small time interval and leads to an explosion.

Structure : An atom bomb consists of a piece of fissile material whose mass is subcritical. This piece has a cylindrical void. It has a cylindrical fissile material which can fit into this void and its mass is also subcritical. When the bomb has to be exploded, this cylinder is injected into the void using a conventional explosive. Now, the two pieces of fissile material join to form the supercritical mass, which leads to an explosion. The structure of an atom bomb.

During this explosion tremendous amount of energy in the form of heat, light and radiation is released. A region of very high temperature and pressure is formed in a fraction of a second along with the emission of hazardous radiation like y rays, which adversely affect the living creatures. This type of atom bombs were exploded in 1945 at Hiroshima and Nagasaki in Japan during the World War II.

Question 5.
What precautions are to he took for those, who are working in radiation laboratories?

1. Radio – Iodine (I131) is used to cure goitre.
4. We should avoid eating while handling radioactive materials.
5. The radioactive materials should be handled only by tongs or by a remote control device.
6. Dosimeters should be worn by the users to check the level of radiation.

Question 6.
What do you know about hydrogen bomb?
Hydrogen bomb is based on the principle of nuclear fusion. A hydrogen bomb is always designed to have an inbuilt atom bomb which creates the high temperature and pressure required for fusion when it explodes. Then, fusion takes place in the hydrogen core and leads to the release of a very large amount of energy in an uncontrolled manner. The energy released in a hydrogen bomb (or fusion bomb) is much higher than that released in an atom bomb (or fission bomb).

Question 7.
What are the applications of radio isotopes in medicine?
Medical applications of radio isotopes can be divided into two parts:

1. Diagnosis
2. Therapy

Radio isotopes are used as tracers to diagnose the nature of circulatory disorders of blood, defects of bone metabolism, to locate tumors, etc., Some of the radio isotopes which are used as tracers are: hydrogen, carbon, nitrogen, sulphur, etc.

1. Radio-sodium (Na24) is used for the effective functioning of heart.
2. Radio-Iodine (I131) is used to cure goiter.
3. Radio-iron is (Fe59) is used to diagnose anaemia and also to provide treatment for the same.
4. Radio-phosphorous (P32) is used in the treatment of skin diseases.
6. Radio-gold (Au198) are used in the treatment of skin cancer.
7. Radiations are used to sterilize the surgical devices as they can kill the germs and microbes.

Question 8.
Mention the applications of radio isotopes in agriculture and industries and archeological research.
Agriculture : The radio isotope of phosphorous (P-32) helps to increase the productivity of crops. The radiations from the radio isotopes can be used to kill the insects and parasites and prevent the wastage of agricultural products. Certain perishable cereals exposed to radiations remain fresh beyond their normal life, enhancing the storage time. Very small doses of radiation prevent sprouting and spoilage of onions, potatoes and gram.

Industries : In industries, radioactive isotopes are used as tracers to detect any manufacturing defects such as cracks and leaks. Packaging faults can also be identified through radio activity. Gauges, which have radioactive sources are used in many industries to check the level of gases, liquids and solids.

1. An isotope of californium (Cf 252) is used in the airlines to detect the explosives in the luggage.
2. An isotope of Americium (Am241) is used in many industries as a smoke detector.

Archeological research : Using the technique of radio carbon dating, the age of the Earth, fossils, old paintings and monuments can be determined. In radio carbon dating, the existing amount of radio carbon is determined and this gives an estimate about the age of these things.

Question 9.
Compare the features of nuclear fission with nuclear fusion.

Question 10.
Mention the preventive measures to be followed while working with radioactive materials.

2. You should avoid eating while handling radioactive materials.
3. The radioactive materials should be handled only by tongs or by a remote control device.
4. Dosimeters should be worn by the users to check the level of radiation.

Question 11.
Write a note on nuclear power plants in India.
Indian Atomic Energy Commission (AEC) was established in August 1948 by the Department of Indian Scientific Research committee at Bombay (now Mumbai) in Maharashtra. It is the nodal agency for all the research done in the field of atomic energy. Dr. Homi Jahangir Bhaba was the first chairman of Indian Atomic Energy Commission. Now, it is known as Bhaba Atomic Research Centre (BARC).

Nuclear power is the fifth largest source of power in India. Tarapur Atomic Power Station is India’s first nuclear power station. Now, there are a total of seven power stations, one each in Maharashtra, Rajasthan, Gujarat, Uttar Pradesh and two in Tamilnadu. In Tamilnadu, we have nuclear power stations in Kalpakkam and Kudankulam. Apsara was the first nuclear reactor built in India and Asia. Now, there are 22 nuclear reactors which are operating in India. Some other operating reactors are

1. Cirus
2. Dhuruva
3. Pumima

Question 12.
Distinguish (i) atom bomb from Nuclear reactor,
(ii) Nuclear fission from Nuclear fusion.
(i) atom bomb from nuclear reactor:

(ii) Nuclear fission from Nuclear fusion

X. Hot Questions.

Question 1.
A neutron is most effective as bulet in nuclear reactions. Why?
This is because a neutron carries no charge. It can hit the nucleus directly without being repelled or attracted by the nucleus or electrons.

Question 2.
Why is $${ _{ 92 } }U^{ 238 }$$ not suitable for chain reaction?
Only fast-moving neutrons of 12 MeV can cause fission of $${ _{ 92 } }U^{ 238 }$$ nuclei. But such neutron has fewer chances of interaction. They escape the fissionable material without causing fission.

Question 3.
Why cadmium is used as control rods in the nuclear reactor?
As Cadmium has a high cross section for absorption of neutrons, cadmium is used as control rod.

Question 4.
Why is nuclear fusion not possible in a laboratory (or) Why is nuclear fusion difficult to carry out?
Nuclear fusion requires a very high temperature of 106 – 107 K. This temperature is attained by causing an explosion due to the fission process. Moreover, no solid container can withstand such a high temperature.

Question 5.
Why is the penetrating power of a – particle is less than that of β – particle?
Ionising power is directly proportional to kinetic energy that varies directly as mass of particle and square of its velocity. Hence ionising power of an alpha particle is more than that of β particle.

Question 6.
Why heavy water is used to slow down the fast moving neutrons?