Radioactivity Worksheets

Radioactivity

Radioactivity is reffered to the particles that are emmited from nuclei as a result of nuclear instability. The word radioactivity is used to describe the subatomic particles. This phenomenon can be observed on heavy metals like uranium and unstable isotopes. Radiactivity was described by Henri Becquerel in 1896.

Here are some questions and answer related to radioactivity.

Worksheet Questions:-

1. Which of the following statements about radioactivity is correct?

(a) It is a nuclear property.
(b) It involves rearrangement of electrons.
(c) Its rate is affected by change in temperature.
(d) Its rate is affected by change in pressure.

2. Who discovered radioactivity for the first time:

(a) Madam Curie
(b) Henry Bacquerel
(c) Neils Bohr
(d) J.J. Thomson

3. The reaction $^8_5 B \to ^8_4Be$ takes place due to

(a) $\alpha$ -decay
(b) Positron decay
(c) Electron capture
(d) $\beta$ -decay

4. Alpha particle is identical to:

(a) Proton
(b) Helium nucleus
(c) Neutron
(d) Electron

5. The penetrating power of $\alpha, \beta \text{and} \gamma$ -rays increases in the order:

(a) $\alpha < \beta < \gamma$
(b) $\alpha < \gamma < \beta$
(c) $\gamma < \alpha < \beta$
(d) $\gamma < \beta < \alpha$

6. $\beta$ -particles have:

(a) Positive charge and negligible mass
(b) Positive charge and some mass
(c) Negative charge and negligible mass
(d) Negative charge and some mass

7. $\gamma$ -rays are essentially:

(a) Electromagnetic radiation
(b) High speed electrons
(c) High speed neutron
(d) High speed helium nucleus

8. Radioactive radiations are

(a) High speed Beryllium atoms
(b) Due to unstable nuclei
(c) Low speed oxygen atoms
(d) Harmless

9. The instrument used in the measurement of radioactivity is:

(a) Cyclotron
(b) G.M. counter
(c) Nuclear reactor
(d) Mass spectrograph

10. Radioactivity is due to:

(a) Stable electronic configuration
(b) Unstable electronic configuration
(c) Stable nucleus
(d) Unstable nucleus

11. The nuclei of same mass number but different atomic number are called:

(a) Isotopes
(b) Isobars
(c) Isomers
(d) Isotones

12. Which of the following has the greatest penetrating power:

(a) $\alpha$ -rays
(b) $\beta$ -rays
(c) $\gamma$ -rays
(d) None of these

13. Which of the following does not have material particle in question:

(a) $\gamma$ -rays
(b) $\alpha$
(c) $\beta$ -particles
(d) None of these

14. If by mistake some radioactive substance gets into the human body, then from point of view of radiation damage the most harmful will be one that emits:

(a) $\gamma$ -rays
(b) Neutron
(c) $\beta$ -particles
(d) $\alpha$ -particles

15. The activity of radioisotopes damages with:

(a) Temperature
(b) Pressure
(c) Chemical environment
(d) None of the above

16. In a reaction $^7_3LI + Z \to ^7_4Be + _0n^1$ the bombarding projectile z in question:

(a) $\alpha$ -particle
(b) Neutron
(c) Proton
(d) Deutron

17. Radioactive disintegration follows:

(a) Zero order reaction
(b) First order reaction
(c) Second order reaction
(d) Third order reaction

18. Which of the following statements in incorrect:

(a) Isobars posses same chemical properties
(b) Isotopes occupy same position in periodic table
(c) Isotopes possess same atomic number
(d) In isobars the total number of protons and neutrons in the nucleus in same

19. Many elements have non-integral atomic masses because:

(a) They have isotopes
(b) Their isotopes have non-integral masses
(c) Their isotopes have different masses
(d) The constituents, neutrons, protons and electrons, combine to give fractional masses

20. Radioactive disintegration differs from a chemical change in being:

(a) An exothermic change
(b) A spontaneous process
(c) A nuclear process
(d) A unimolecular first order reaction

21. $^{20}_{10}Ne \text{and} ^{22}_{10}Ne$ are two isotopes of neon. Which of the following statements is incorrect for them:

(a) Both have the same atomic number
(b) Both have the same number of electrons
(c) Both have the same number of neutrons
(d) Both have the same number of protons

22. Tan isotone of $^{76}_{32}Ge$ is:

(a) $^{77}_{32}Ge$

(b) $^{87}_{33}As$

(d) $^{78}_{34}Se$

23. Which of the following has the highest value of its radioactivity:

(a) 1 g Ra
(b) $1g RaCl_2$
(c) $1 g RaSO_4$
(d) $1 g Ra_3 (PO_4)_2$

24. The reaction $^2_1D + ^3_1T \to ^4_2He + ^1_0n$ is an example of:

(a) Nuclear fission
(b) Nuclear fusion
(c) Ratio disintegration
(d) Artificial radio activity

25. Radioactive iodine is being used to diagnose the disease of:

(a) Bones
(b) Blood cancer
(c) Thyroid
(d) Kidney

26. Out of various isotopes of hydrogen, deuterium is:

(a) Radioactive
(b) non-radioactive
(c) heaviest
(d) lightest

27. an isobar of $^{40}_{20}Ca$ is:

(a) $^{40}_{18}Ar$

(b) $^{38}_{20}Ca$

(d) $^{42}_{20}Ca$

28. During a $\beta$ -decay the mass of the atomic nucleus:

(a) Increase by one unit
(b) Decreases by one unit
(c) Increases by two units
(d) Decreases by two units

29. The elements $^{32}_{16}S, ^{31}_{15}P \text{and} ^{30}_{14}Si$ are called:

(a) Isotopes
(b) Isobars
(c) Isotones
(d) Isomers

30. The triad of nuclei that is isotonic:

(a) $^{14}_6C, ^{15}_7N, ^{17}_9F$

(b) $^{12}_6C, ^{14}_7N, ^{17}_9F$

(d) $^{14}_6C, ^{14}_7N, ^{19}_9F$

31. Which one of the following pairs represents isobars:

(a) $_2He^3, _2He^4$

(b) $_{12}Mg^{24}, _{12}Mg^{25}$

(d) $_{19}K^{40}, _{18}Ar^{40}$

32. The $\beta$ -decay of $^{24}_{11}Na$ produces an isotopes of:

(a) Na
(b) Al
(c) Mg
(d) Ne

33. When $^{226}_{88}Ra$ emits an $\alpha$ -particle, a new element is formed. In which of the group in periodic table does it fall?

(a) Zero group
(b) II group
(c) III group
(d) IV group

34. Which has maximum n / p ratio:

(a) $^{16}N$
(b) $^{16}F$
(c) $^{16}O$
(d) $^{16}Ne$

35. The number of neutrons in the parent nucleus which gives $^{14}N$ on beta emission is:

(a) 6
(b) 7
(c) 8
(d) 14

36. After the emission of an $\alpha$ -particle from the atom $^{238}_{92}X$ the number of neutrons in the atom will be:

(a) 138
(b) 140
(c) 144
(d) 150

37. An element A decays into C by a two step process:
$A \to B + ^4_2He \\ B \to C + 2 ^0_{-1}e$ Then

(a) A and B are isobars
(b) A and C are isotopes
(c) A and C are isobars
(d) A and B are isotopes

38. Isotopes contain:

(a) Same number of neutrons
(b) Same number of electrons
(c) Same mass number
(d) None of the above

39. Which of the following is not an isotope of hydrogen?

(a) Tritium
(b) Deuterium
(c) Ortho hydrogen
(d) None of the above

40. Magnet will cause greatest deflection of:

(a) X-rays
(b) $\beta$ -rays
(c) $\alpha$ -rays
(d) Neutrons

41. Which one of the following radiations is most easily stopped by air:

(a) $\alpha$ -rays
(b) $\beta$ -rays
(c) $\gamma$ -rays
(d) X-rays

42. Which leaves no track on Wilson cloud chamber:

(a) Electrons
(b) Protons
(c) $\alpha$
(d) Neutrons

43. When any atom emits one $\alpha$ -particle, then:

(a) Atomic number is changed by 2 units but atomic mass remains unchanged
(b) Atomic mass is changed by 2 units but atomic number remains unchanged
(c) Atomic number is decreased by 2 units and atomic mass is decreased by 4 units
(d) Atomic mass is decreased by 2 units and atomic number is decreased by 4 units

44. The half life of a radioactive element is one year. If we have initially one gram of the element, the number of grams of the element left after five years.

(a) 1/5
(b) 1/32
(c) 1/2
(d) 1/23

45. Which of the following nucleides has magic number of both protons and neutrons:

(a) $^{115}_{50}Sn$

(b) $^{207}_{82}Pb$

(d) $^{118}_{50}Sn$

46. Which rays are not emitted by radium:

(a) $\alpha$ -rays
(b) $\beta$ -rays
(c) $\gamma$ -rays
(d) X-rays

47. The symbol X in the following equation $^{23}_{11}Na + ^1_1H \to ^{23}_{12}Mg + X$ is:

(a) Positron
(b) Neutron
(c) Deutron
(d) $\alpha$ -particle

48. An element A changes to B by the emission of one $\alpha$ -particle and two $\beta$ -particles. A and B are:

(a) Isotopes
(b) Isobar
(c) Isotone
(d) Nuclide

49. The symbol of the nucleus which is obtained by the emission of $\beta$ -particles from $^{35}_{17}Cl$ :

(a) $^{35}_{18}Ar$

(b) $^{35}_{17}Ar$

(d) $^{37}_{17}Ar$

50. Which is correct statement here?

(a) Electron, positron both have same mass
(b) Atom bomb, H-bomb both are examples of Nuclear fission
(c) The lesser $t_{1/2}$ lesser is the no. of atoms undergoing decay in a given time
(d) All are correct statements

51. Out of the three isobars $^{73}_{31}Ga, ^{73}_{32}Ge \text{and} ^{73}_{33}As$ the second is stable, $^{73}_{31}Ga$ is likely to be:

(a) A negative $\beta$ emitter
(b) A positron emitter
(c) Also stable
(d) Both positron and electron emitter

52. Phenomenon of Radioactivity arises from:

(a) Binary fission
(b) Nuclear fusion
(c) Decay of un-stable nuclei]
(d) None of these

53. The uranium (mass number 238 and atomic number 92) emits an $\alpha$ -particle, the product has the mass number and atomic number:

(a) 236 and 92
(b) 234 and 90
(c) 238 and 90
(d) 236 and 90

54. The radiations from a naturally occurring radioactive substance, as seen after deflection by a magnetic field in one direction are:

(a) Definitely alpha rays
(b) Definitely beta rays
(c) Both alpha and beta rays
(d) Either alpha or beta rays

55. The element produced by the emission of an $\alpha$ -particle from $^{226}_{88}Ra$ is:

(a) $^{222}_{88}Ra$

(b) $^{222}_{86}Rn$

(d) $^{226}_{89}Ac$

56. The element produced by the emission of an $\beta$ -particle from $^{234}_{90}Th$

(a) $^{204}_{82}Pb$

(b) $^{234}_{91}Pa$

(d) $^{235}_{92}U$

57. The isotope of elements was discovered by:

(a) Soddy
(b) Thomson
(c) Curie
(d) Chadwick

58. During the fission of $^{235}U$ , the product will have a mass:

(a) > $^{235}U$
(b) < $^{235}U$
(c) Equal to $^{235}U$
(d) May be any of these three

59. An element with atomic number 90 and mass number 232 loses one alpha and two beta particles successively. The resulting element will have:

(a) At. no. 90 and mass no. 228
(b) At. no. 88 and mass no. 230
(c) At. no. 86 and mass no. 224
(d) At. no. 90 and mass no. 226

60. The isotope of $^{231}Th$ can be converted into $^{227}Th$ by the emission of:

(a) One $\alpha$ -particle
(b) Four $\beta$ particles
(c) Two $\alpha$ and two $\beta$ particles
(d) One $\alpha$ and two $\beta$ particles

61. An element with at. no. 84 and mass no. 218 loses one $\alpha$ and two $\beta$ –particles in three successive stages, the resulting element will have:

(a) At. no. 84 and mass no. 214
(b) At. no. 82 and mass no. 214
(c) At. no. 84 and mass no. 218
(d) At. no. 92 and mass no. 218

62. In the following radioactive decay $_{92} X ^{232} \to _{89} Y^{220}$ how many $\alpha \text{and} \beta$ particles are ejected by X and Y to form Y:

(a) $3 \alpha \, \text{and} 3 \beta$
(b) $5 \alpha \, \text{and} 3 \beta$
(c) $3 \alpha \, \text{and} 5 \beta$
(d) $5 \alpha \, \text{and} 5 \beta$

63. The number of $\alpha \text{and} \beta$ particles emitted in the nuclear reaction $^{228}_{90}Th \to ^{212}_{83} Bi$ are:

(a) $4 \alpha \text{and} 1 \beta$
(b) $3 \alpha \text{and} 7 \beta$
(c) $8 \alpha \text{and} 1 \beta$
(d) $4 \alpha \text{and} 7 \beta$

64. Which of the following is used to bombard $_{13}Al^{27}$ to give $_{15}P^{30}$ and a neutron:

(a) $\alpha$ -particle
(b) $\beta$ -particle
(c) Proton
(d) Deutron

65. If the amount of radioactive substance is increased three times, the number of atoms disintegrated per time would:

(a) Be double
(b) Be triple
(c) Remain one third
(d) Not change

66. An $\alpha$ -particle is given out by $_{92}X^{238}$ . The new species Y should be:

(a) $_{92}Y^{234}$
(b) $_{90}Y^{238}$
(c) $_{92}Y^{234}$
(d) $_{94}Y^{234}$

67. During $\beta$ -decay:

(a) An atomic electron is ejected
(b) An electron which is already present within the nucleus is ejected
(c) A part of the nuclear binding energy is converted into electron
(d) A neutron in the nucleus decays emitting an electron

68. $^{31}_{15}P$ is an isotone of:

(a) $^{35}_{17}Cl$

(b) $^{31}_{16}S$

(d) $^{28}_{14}Si$

69. When a radioactive nucleus emits an alpha particle the mass number of the atom:

(a) Increases and it’s at .no. decreases
(b) Decreases and it’s at. no. decreases
(c) Decreases and it’s at. no. increases
(d) Remains same and it’s at. no. decreases

70. Half life period of sodium is 1620 years. In how many years 1 g will remain 0.25 g:

(a) 3240 year
(b) 1620 year
(c) 810 year
(d) 405 year

71. After losing a number of $\alpha \text{and} \beta$ particles $^{238}_{92}U$ changes to $^{206}_{82}Pb$ . The total number of $\alpha$ particles lost in this process is:

(a) 10
(b) 5
(c) 8
(d) 32

72. The relationship between the size of the nucleus (R) and its mass number (A) may be given by:

(a) $R = R_0A$
(b) $R = R_0A^{1/2}$
(c) $R = R_0A^{1/3}$
(d) $R = R_0A^{1/4}$

73. $_{84}Po^{210} \to _{82}Pb^{206} + _2He^4$ . In this reaction predict the position of group of Po when lead is in IVA group:

(a) IIA
(b) IVB
(c) VIB
(d) VIA

74. One gram of a substance has 10 hr. half life. What is the half life present in two gram:

(a) 10 hr.
(b) 15 hr.
(c) 20 hr.
(d) 40 hr.

75. The last product of 4n series is:

(a) $_{82}Pb^{208}$
(b) $_{82}Pb^{207}$
(c) $_{82}Pb^{209}$
(d) $_{82}Pb^{205}$

76. The reaction $_5^8B \to ^8_4Be + ^ 0_{+1}e$ takes place due to:

(a) Alpha decay
(b) Beta decay
(c) Positron decay
(d) Electron capture

77. After the emission of $3 \alpha \text{and} 3 \beta$ particles from $^{235}_{92}U$ , we get:

(a) $^{223}_{89}Ac$

(b) $^{225}_{89}Ac$

(d) $^{229}_{89}Ac$

78. The first non-active light element which was shown to exhibit isotopy was:

(a) Hydrogen
(b) Helium
(c) Neon
(d) Lithium

79. An element has at. no. 84 and mass no. 218. It displaces $1 \alpha \text{and} \beta$ particles. The resultant element will have:

(a) At. no. 78 and mass no. 218
(b) At. no. 84 and mass no. 218
(c) At. no. 84 and mass no. 214
(d) At. no. 81 and mass no. 210

80. Which one of the following statements is wrong?

(a) Isobars of any element cannot be identical
(b) Isotopes of any element may be same
(c) All atoms of the any element have same mass number
(d) Isotope of one element may be isobar of the other element

81. Which of the following is used in cancer treatment:

(a) $U^{238}$
(b) $Co^{60}$
(c) $He^4$
(d) $Br^{80}$

82. $_1H^2 + _1H^2 \to _2He^3 + _0n^1$
The above nuclear reaction is called

(a) Nuclear fission
(b) Nuclear fusion
(c) Artificial transmutation
(d) Spontaneous reaction

83. The half life period of a radioactive element is 120 days. After 480 days 4.0 g of the element will be reduced to (….)g.:

(a) 2.0
(b) 1.0
(c) 0.5
(d) 0.25

84. A radioisotope has half life of 10 days. If today there is 125 g of it left what was its mass 40 days earlier:

(a) 600 g
(b) 1000 g
(c) 1250 g
(d) 2000 g

85. A radioactive element has a half life of 20 min. how much time should lapse before the element is reduced to 1/8 of its original mass:

(a) 40 min.
(b) 60 min.
(c) 80 min.
(d) 160 min.

86. Which of the following particles is considered to be responsible for keeping nucleons together?

(a) Protons
(b) Mesons
(c) Neutrons
(d) Positrons

87. If 8.0 g of a radioactive isotope has a half life of 10 hr, the half life of 2.0 g of the same substance is:

(a) 2.5 hr
(b) 5 hr
(c) 10 hr
(d) 40 hr

88. The half life of a radioactive element depends upon:

(a) The amount of the element
(b) The temperature
(c) The pressure
(d) None of the above

89. A sample of rock from moon contains equal number of atoms of uranium and lead ( $t_{1/2} \text{for} U = 4.5 \times 10^{9}$ years) the age of the rock would be:

(a) $4.5 \times 10^9$ years
(b) $9.0 \times 10^9$ years
(c) $13.5 \times 10^9$ years
(d) $2.25 \times 10^9$ years

90. The half life period of a radioactive element is 140 days. After 560 days, one gram of the element will reduce to:

(a) 1/2 g
(b) 1/4 g
(c) 1/8 g
(d) 1/16 g

91. The sum of the number of neutrons and protons in the isotope of hydrogen is:

(a) 6
(b) 5
(c) 4
(d) 3

92. One of three isobars $^{114}_{48}Cd, ^{114}{49}In$ and $^{114}_{50}Sn$ , the one which is likely to be radioactive is:

(a) $^{114}{49}In$

(b) $^{114}_{48}Cd$

(d) Cannot be said

93. $C^{12}, C^{13} \text{and} C^{14}$ are:

(a) Isobars
(b) Allotropes
(c) Isotopes
(d) None of the above

94. Control rods used in nuclear reactors are made of:

(a) Beryllium
(b) Aluminium
(c) Uranium
(d) Graphite

95. Which metal Aprons are worn by radiographer of protect him from radiation:

(a) Mercury coated apron
(b) Copper apron
(c) Lead apron
(d) Aluminium apron

96. A radioactive element has a half life of one day. After three days the amount of the left will be:

(a) 1/2 of the original amount
(b) 1/4 of the original amount
(c) 1/8 of the original amount
(d) 1/10 of the original amount

97. One gram of a sample of radioactive element decays to 0.5 g in 5000 years. The decay constant of the element is:

(a) $1.4 \times 10^{-4} yr^{-1}$
(b) $2 \times 10^{-3} yr^{-1}$
(c) $2 \times 10^{-5} yr^{-1}$
(d) $2 \times 10^{-4} yr^{-1}$

98. Which of the following is used in dating archeological findings:

(a) $^{235}_{92}U$

(b) $^{14}_{6}C$

(d) $^{65}_{26}Fe$

99. Last product in (4n + 2) radioactive disintegration series is:

(a) $Pb^{208}$

(b) $Pb^{207}$

(d) $Pb^{206}$

100. The half life of an element is 30 minutes. After how much time, the amount of the element left is 1/16th of the original amount:

(a) One hours
(b) 16 hours
(c) Four hours
(d) Two hours

101. Strength of nuclear forces as compared to electrostatic forces is:

(a) $10^{-12}$ times
(b) $10^{12}$ times
(c) $10^{21}$ times
(d) $10^{-20}$ times

102. The half life period of a radioactive nucleus:

(a) Depends upon the temperature of the atom
(b) Is reciprocal to the radioactive decay constant
(c) Is constant for all radioactive elements
(d) Is always less than unity

103. The decay constant of a radioactive sample is $\lambda$ . The half life and mean life of the radioactive substance are respectively:

(a) $\dfrac{1}{\lambda}; in \dfrac{2}{\lambda}$
(b) $\dfrac{In 2}{\lambda}; \dfrac{1}{\lambda}$
(c) $\lambda In 2, \dfrac{1}{\lambda}$
(d) $\dfrac{\lambda}{In 2}; \dfrac{1}{\lambda}$

104. The end product of (4n + 1) radioactive disintegration series is:

(a) $_{84}Po^{210}$
(b) $_{82}Pb^{208}$
(c) $_{82}Pb^{207}$
(d) $_{83}Bi^{209}$

105. The half life of $^{14}$ is ………………… if its $\lambda \text{is} 2.31 \times 10^{-4} yr^{-1}$

(a) $2 \times 10^2$ yrs.
(b) $3.5\times 10^4$ yrs.
(c) $4 \times 10^3$ yrs.
(d) $3 \times 10^4$ yrs.

106. The half life of a radioactive substance is 10 years. After 40 years mass left is:

(a) 6. 25%
(b) 12.5%
(c) 25%
(d) 100%

107. The half life period of $^{232}_{90}Th \, \text{is} 1.3 \times 10^{10}$ yrs. $1.0 \times 10^{-3}kg$ of this will be reduced to $5.0 \times 10^{-4}kg$ in:

(a) $1.3 \times 10^{10}$
(b) $0.65 \times 10^{10}$
(c) $2.6 \times 10^{10}$
(d) $0.65 \times 10^{5}$

108. The half life period of a radioactive isotope is 34.65 s. the decay constant is:

(a) $2 \times 10^{-2} s^{-1}$
(b) $2.0 \times 10^{-3} s^{-1}$
(c) $4.0 \times 10^{-8} s^{-1}$
(d) $2.0 \times 10^{-4} s^{-1}$

109. After 2 hrs the amount of a radioactive substance is reduced to 1/16 of its original amount. The half life of the radioactive substance is:

(a) 15 min.
(b) 30 min.
(c) 45 min
(d) 60 min.

110. The half life of a radioactive element is 35 yrs. If there are $4 \times 10^6$ nuclei at the start then after how many years these will be left $0.5 \times 10^6$ nuclei?

(a) 140
(b) 105
(c) 70
(d) 35

111. Which one of the following pairs represents isobars?

(a) $_1^3H, ^3_2He$

(b) $_1^2H, ^2_1H$

(d) $_{17}^{35}Cl, ^{37}_{17}Cl$

112. The $t_{1/2}$ of a radioactive substance is 8yrs. After 16 yrs the mass of the substance will reduce from starting 16.0 g to:

(a) 8 g
(b) 6 g
(c) 4 g
(d) 2 g

113. $^{14}_6C$ has a half-life of 5760 years. 100 mg of a smple is reduced to 12.5 mg in:

(a) 11520 years
(b) 1440 years
(c) 17,280 years
(d) 2880 years

114. The cobalt isotope of mass 60 decays with a half-life of 5.3 years. How many years will it take for of a sample of 500 g of cobalt-60 to disintegrate to 7/8?

(a) 10.6
(b) 4.6
(c) 15.9
(d) 9.2

115. If one starts with 1 curie of radioactive substance $(t_{1/2} = 12 hrs)$ the activity left after a period of 1 week will be about:

(a) 1 curie
(b) 120 micro curie
(c) 60 micro curie
(d) 8 millicurie

116. A radioactive sample has a half-life of 1500 yrs. After 3000 yrs sealed tube containing 1 g of the sample will contain:

(a) 1 g of the sample
(b) 0.5 g of the sample
(c) 0.25 g of the sample
(d) 0.00 g of the sample

117. A radioactive isotope decays at such a rate that after 96 minutes only 1/8 of the original amount remains, the half-life of the nuclide in minutes is:

(a) 12.0
(b) 24.0
(c) 32.0
(d) 48.0

118. The half life period of a radioactive element is 69.3 s. the value of the disintegration constant is:

(a) $1.0 s^{-1}$
(b) $0.1 s^{-1}$
(c) $0.01 s^{-1}$
(d) $0.001 s^{-1}$

119. Radium has atomic mass $226 g mol^{-1}$ and a half-life of 1600 yrs. The number of disintegrations produced per second from one gram is:

(a) $4.8 \times 10^{10}$
(b) $9.2 \times 10^{6}$
(c) $3.7 \times 10^{10}$
(d) Zero

120. The half-life period of radium is 1600 yrs. In how much time 1 g sample of radium reduces to 125 mg:

(a) 800 yrs.
(b) 1600 yrs.
(c) 2400 yrs.
(d) 4800 yrs.

121. Which element is the end product of each natural radioactive series:

(a) Sn
(b) Bi
(c) Pb
(d) C

122. The two nuclides $_ZA^m \text{and} _{Z-2}B^{m-4}$ are known as:

(a) Isotones
(b) Nuclear isomers
(c) Isoters
(d) Isodiaphers

123. Atom bomb is based on:

(a) Nuclear fission
(b) Nuclear fusion
(c) Natural radioactivity
(d) Artificial disintegration

124. On which of the following principles hydrogen bomb is based:

(a) Nuclear fission
(b) Natural radioactivity
(c) Nuclear fusion
(d) Artificial radioactivity

125. Half life of an element falls to 1/10 after 2.303 s. the half-life period of the element is:

(a) 2.303 s
(b) 0.2303 s
(c) 0.693 s
(d) 0.0693 s

126. Half life of a radioactive disintegration $(A \to B)$ having rate constant $231 s^{-1}$ is:

(a) $3.0 \times 10^{-2} s$
(b) $3.0 \times 10^{-3} s$
(c) $3.3 \times 10^{-2} s$
(d) $3.3 \times 10^{-3} s$

127. The half lie of $_{92}U^{238} \text{is} 4.5 \times 10^9$ years. After how many years, the amount of $_{92}U^{238}$ will be reduced to half of its present amount:

(a) $9.0 \times 10^9$ years
(b) $13.5 \times 10^9$ years
(c) $4.5 \times 10^9$ years
(d) $4.5 \times 10^{4.5}$ years

128. The masses of neutron and proton are 1.0087 and 1.0073 a.m.u. respectively. If the neutrons and protons combine to form helium of mass 4.0015 a.m.u., the binding energy of the helium nucleus will be:

(a) 28. 4 MeV
(b) 20. 8 MeV
(c) 27. 3 MeV
(d) 14. 2 MeV

129. Which of the following projectiles is the best for bombarding the nuclide?

(a) $\alpha$ -particles
(b) Proton
(c) Deutron
(d) Neutron

130. Stable nuclides are those whose n/p ratio is:

(a) > 1
(b) < 1
(c) 2
(d) 1

131. The first artificial transmutation of elements was carried out by:

(a) I. Curie
(b) P. Curie
(c) Rutherford
(d) Soddy

132. A possible material for use in nuclear reactor as fuel is:

(a) Thorium
(b) Zirconium
(c) Beryllium
(d) Plutonium

133. Heavy water is used as a moderator a nuclear reactor. The function of the moderator is:

(a) To slow down the neutrons to thermal energy
(b) To control the energy released in the reactor
(c) To absorb neutrons and stop chain reaction
(d) To cool the reactor

134. In nuclear reactors heavy water is used as a:

(a) Fuel
(b) Projectile
(c) Moderator
(d) Arrestor

135. Fuel used in atomic reactor is:

(a) Thorium
(b) Sodium
(c) Uranium
(d) Petroleum

136. High temperature of sun is due to:

(a) Nuclear fusion of helium
(b) Nuclear fission of helium
(c) Nuclear fusion of hydrogen
(d) None of these

137. Packing fraction may be expressed as:

(a) $\dfrac{\text{isotopic mass- mass number}}{\text{mass number}} \times 10^4$

(b) $\text{isotopic mass- isotopic mass number}\times 10^4$

(d) $\dfrac{\text{ mass number - isotopic mass }}{\text{isotopic number}} \times 10^4$

138. The number of $\beta$ -particles emitted when $^{238}_{92}U$ is finally converted into $^{206}_{82}Pb$ is:

(a) 2
(b) 4
(c) 8
(d) 6

139. The masses of neutron and proton are 1.0087 and 1.0073 a.m.u. respectively. If the neutrons and protons combine to form helium nucleus of mass 4.0015 a.m.u. the mass defect will be:

(a) 0.3050 amu
(b) 0.3005 amu
(c) 0.0030 amu
(d) 0.0003 amu

140. $^{235}_{92}U$ is a member of actinium series. Another member of the same series is:

(a) $^{232}_{90}Th$
(b) $^{219}_{86}Rn$
(c) $^{232}_{89}Ac$
(d) $^{209}_{83}Bi$

141. The minima in the packing fraction curve is occupied by:

(a) C
(b) Ca
(c) Fe
(d) U

142. The thermal neutrons have energy of the order:

(a) 100 MeV
(b) 1 MeV
(c) 100 eV
(d) Fraction of eV

143. Which one of the following nuclei is fissionable but not fissible:

(a) $^{233}_{92}U$

(b) $^{235}_{92}U$

(d) $^{239}_{94}U$

144. The decomposition of a compound nucleus depends upon:

(a) Its energy
(b) Its mode of formation
(c) Its atomic number
(d) The projectile used in its formation

145. If the total binding energies $^2_1H, ^4_2He, ^{56}_{26}Fe \text{and} ^{235}_{92}U$ nuclei are 2.22, 28.2 492 and 1786 MeV respectively identify the most stable nucleus out of the following

(a) $^4_2He$

(b) $^{235}_{92}U$

(d) $^{56}_{26}Fe$

146. In the reaction, $^{10}_5B + ^4_2He \to X + ^1_0n$ , X is:

(a) Nitrogen
(b) Fluorine
(c) Positron
(d) Electron

147. The disintegration of $^{14}N \text{into} ^{14}C$ is due to the emission of:

(a) Proton
(b) Neutron
(c) Positron
(d) Electron

148. The missing particle in the reaction $^{253}_{99}Es + ^4_2He \to ^{256}_{101}Md + \cdots \cdots$ is:

(a) Deutron
(b) Proton
(c) Neutron
(d) $\beta$ -particle

149. According to the nuclear reaction $_4Be + ^4_2He \to ^{12}_6C + ^1_0n$ the mass number of Be atom is:

(a) 4
(b) 6
(c) 8
(d) 9

150. Which of the following belongs to 4n + 1 series?

(a) Bi-212
(b) Bi-213
(c) Bi-211
(d) Bi-214

151. Nuclear reaction accompanied with emission of neutron (s) is:

(a) $^{27}_{13}Al + ^4_2He \to ^{31}_{15}P$

(b) $^{12}_6C + ^1_1H \to ^{13}_7$

(d) $^{241}_{96}Am + ^4_2He \to ^{244}_{97}Bk + ^0_{+1}e$

152. $_{15}Al^{28}$ when irradiated by a suitable projectile gives $_{15}P^{31}$ and a neutron. The projectile used is:

(a) $_0n^1$
(b) $_1H^1$
(c) $_2He^4$
(d) $_1He^2$

153. Which one of the following nuclear reaction is wrong:

(a) $^7_3Li + ^1_1H \to ^7_4Be + ^1_0n$

(b) $^{45}_{21}Sc + ^1_0n \to ^{45}_{20}Ca + ^1_0n$

(d) $^{202}_{83}Bi + ^2_1H \to ^{203}_{84}Po + ^1_0n$

154. 1 a.m.u. is equivalent to:

(a) 931 MeV
(b) 100 J
(c) 931 kcal
(d) $10^7$ erg

155. Which of the following has maximum velocity

(a) Positron
(b) $\gamma$ -rays
(c) $\alpha$ -particles
(d) $\beta$ -particles

156. In the reaction $_{13}Al^{27} + _2He^4 \to _{15}P^{30} + ?$ the absent particle is:

(a) $_{-1}e^0$
(b) $_1e^0$
(c) $_0n^1$
(d) $\gamma$ -rays

157. In a nuclear reaction the energy absorbed or evolved is usually expressed as:

(a) MeV / nucleon
(b) MeV / mole
(c) Kcal / mol
(d) MeV

158. In a nuclear reaction between a deutron and $^{12}_6C; ^{13}_{7}N$ is produced. Which is the other particle liberated?

(a) Electron
(b) Proton
(c) Positron
(d) Neutron

159. When one microgram of matter is converted into energy, the amount of energy released will be:

(a) $9 \times 10^{14}J$
(b) $9 \times 10^{10}J$
(c) $9 \times 10^{7}J$
(d) $3 \times 10^{14}J$

160. The $^{14}_6C$ in upper atmosphere is generated by the nuclear reaction:

(a) $^{14}_7N + ^1_1H \to ^{14}_6C + ^0_{+1}e + p$

(b) $^{14}N \to ^{14}_6C + ^0_{+1}e$

(d) $^{14}_7N + ^1_1H \to ^{14}_6C + ^4_2He$

161. In carbon dating the isotope of carbon used is:

(a) $^{12}_6C$

(b) $^{13}_6C$

(d) $^{13}_6C \text{and} ^{14}_6C$

162. $^{238}_{92}U \overset{\alpha}{\rightarrow} A \overset{\beta}{\rightarrow} ^y_xB$ . What are x and y?

(a) 90, 234
(b) 91, 234
(c) 92, 234
(d) 93, 234

163. $_ZX^M + _2He^4 \to _{15}P^{30} + _0n^1$

(a) Z = 13, M = 27
(b) Z = 13, M = 28
(c) Z = 12, M = 27
(d) Z = 12, M = 17

164. $Co^{60}$ isotope is used in:

(a) The treatment of heart
(b) The treatment of skin
(c) The treatment of diabetes
(d) The treatment of cancer

165. The future inexhaustible source of energy will be:

(a) Hydrogen
(b) Uranium
(c) Coal
(d) Natural gas

166. What is the total binding energy of $^{14}_7N$ . Its nuclear mass is 14.0031 amu. The masses of proton and neutron are 1.0078 amu and 1.0087 amu respectively. $1 amu = 1.66 \times 10^{-24}g, 1MeV = 1.6 \times 1.6 \times 10^{-6}ergs, c = 3.0 \times 10^8m s^{-1}$ . It is nearly:

(a) 95 MeV
(b) 100 MeV
(c) 105 MeV
(d) 120 MeV

167. When a radioactive isotope has a greater proton / neutron ratio than that of the stable isotope. It emits:

(a) $\gamma$ -rays
(b) $\beta$ -rays
(c) neutron
(d) positron

168. a negative value for packing fraction indicates that the isotope is:

(a) unstable
(b) stable
(c) radioactive
(d) artificial

169. half life of radium is 1580 years. Its average life will be:

(a) $2.275 \times 10^3 years$
(b) $0.25 \times 10^2 years$
(c) $1.8 \times 10^3 years$
(d) $2.5 \times 10^3 years$

170. In the nuclear reactors, the speed of the neutrons is slowed down by:

(a) Heavy water
(b) Ordinary water
(c) Zinc rod
(d) Caustic soda

171. For treatment of cancerous tumors, the radio isotope used is:

(a) Co-60
(b) Th-231
(c) U-35
(d) Pu-239

172. If in two minutes a radioactive substance reduces by 75%. Its decay constant is:

(a) $0.0115 s^{-1}$
(b) $0.01155 s^{-1}$
(c) $0.0225 s^{-1}$
(d) $0.01555 s^{-1}$

173. In chlorine gas ratio of $^{35}Cl \text{and} ^{37}Cl$ is:

(a) 1 : 3
(b) 3 :1
(c) 1 : 1
(d) 1 : 4

174. Graphite is used in nuclear reactor as:

(a) Making lining in furnace
(b) Lubricant
(c) Reducer of neutron velocity
(d) Fuel

175. The method which uses radioactivity for determining the age of a prehistoric fossil is called:

(a) Uranium dating
(b) Deuterium dating
(c) Radium dating
(d) Carbon dating

176. Radium emits:

(a) $\alpha$ -rays
(b) $\beta$ -rays
(c) $\gamma$ -rays
(d) $\alpha, \beta \text{and} \gamma$ -rays

177. Identify the nuclear fusion process:

(a) $^2_1H + ^3_1H \to ^4_2He + ^1_0n$

(b) $^{30}_{15}P \to ^{30}_{14}Si + 0_{+1}e$

(d) $^{59}_{29}Cu\to ^{58.69}_{28}Ni + ^0_{+1}e$

178. Radioactive decay process does not lead to the transformation of an element into another in case of one of the emission:

(a) $\alpha$
(b) $\beta^-$
(c) $\beta^+$
(d) $\gamma$

179. An isotope of parent element is produced when it loses:

(a) One $\alpha$ -particle
(b) One $\beta^-$ -particle
(c) One $\beta^-$ and two $\beta^-$ particle
(d) Tow $\beta^-$ and one $\beta^-$ particle

180. In the following nuclear equation $^{14}_7N + \alpha \to \text{proton + missing product}$ . The missing product is:

(a) $^{16}_8O$

(b) $^{17}_8O$

(d) $^{15}_8O$

181. Positron is:

(a) Electron with positive charge
(b) Helium nucleus
(c) A nucleus with tow protons
(d) A nucleus with one neutron and one proton

182. Which is not emitted by radioactive substance:

(a) $\alpha$ -rays
(b) $\beta$ -rays
(c) Positron
(d) Proton

183. Which one of the following mass numbers of uranium is the most reactive:

(a) 235
(b) 236
(c) 237
(d) 238

184. C-14 is used in carbon dating of dead objects because:

(a) Its half life is 1000 years
(b) Its half life is 10000 years
(c) It is found in nature abundantly and in definite ratio
(d) It is found in dead animals abundantly

185. An element has two main isotopes of mass numbers 85 and 87. The abundance is 75% and 25% respectively. The atomic weight of the element is:

(a) 86.0
(b) 86.5
(c) 85.7
(d) 85.5

186. $^{235}_{92}U + ^1_0n \to ^{236}_{92}U \to \text{fission products + neutrons} + 3.2 \times 10^{-11}J$ . The energy released when 1 g of $^{235}_{92}U$ finally undergoes fission is:

(a) $8.2 \times 10^7kJ$
(b) $9.2 \times 10^7kJ$
(c) $12.75 \times 10^8kJ$
(d) $16.4 \times 10^8kJ$

187. The basis of C-14 dating method is that the:

(a) C-14 fraction is the same in all objects
(b) C-14 is highly unstable and is readily lost from the objects
(c) The ratio of C-14 and C-12 in our atmosphere has always been constant.
(d) Living tissue will not absorb C-14 but will absorb C-12 from its source of carbon

188. Which one is the correct nuclear reaction:

(a) $_6C^{13} + _1H^1 \to _7N^{13} + \beta^- + \gamma$
(b) $_{11}Na^{23} + _1H^1 \to _{10}Ne^{20} + _2He^4$
(c) $_{13}Al^{27} + ^1_0n \to _{11}Na^{23} + 2 _{-1}e^0$
(d) $_{12}Mg^{28} + _2He^4n \to _{13}Al^{27} + _0n^1$

189. Radioactive decay is:

(a) A physical change
(b) A chemical change
(c) A nuclear change
(d) None of these

190. In radioactive decay the emitted electrons come from:

(a) Nucleus of the atom
(b) Inner orbit of the atom
(c) Outermost orbit of the atom
(d) Orbit having principal quantum number one

191. Decrease in atomic number is not observed during:

(a) Alpha emission
(b) Beta emission
(c) Positron emission
(d) Electron capture

192. Thorium disintegration series is known as:

(a) (4n + 2) series
(b) (4n + 3) series
(c) (4n) series
(d) (4n + 1) series

193. Which one of the following is wrong nuclear reaction?

(a) $_{96}Cm^{242} (\alpha, 2n) _{97}Bk^{243}$

(b) $_5B^{10} (\alpha, n) _7N^{13}$

(d) $_{14}Si^{28} (d, n) _{15}P^{29}$

194. The number of neutrons accompanying the formation of $_{54}Xe^{139} \text{and} _{38}Sr^{94}$ from the absorption of a slow neutron by $_{92}U^{235}$ followed by nuclear fission is:

(a) 0
(b) 1
(c) 2
(d) 3

195. The atomic mass of an element is 12.00719 a.m.u. if there are 6 neutrons in the nucleus of the atom of the element, the binding energy per nucleon of the nucleus will be:

(a) 7.64 MeV
(b) 76.4 MeV
(c) 764 MeV
(d) 0.764 MeV

196. In the following nuclear reactions: $_7N^{14} + _2He^4 \to _8O^{17} + X_1 \text{and} _{13}Al^{27} + _1H62 \to _{14}Si^{28} + X_2, X_1 \text{and} X_2$ are respectively:

(a) $_1H^1 \text{and} _0n^1$

(b) $_0n^1\text{and} _1H^1$

(d) $_0n^1\text{and} _2He^4$

197. $_{95}Am^{241} \text{and} _{90}Th^{234}$ belong respectively to:

(a) 4n and (4n +1) radioactive disintegration series
(b) (4n + 1) and (4n + 2) radioactive disintegration series
(c) (4n + 1) and (4n + 3) radioactive disintegration series
(d) (4n +1) and 4n radioactive disintegration series

198. In the sequence of the following nuclear reactions:
$_{92}X^{238} \overset{-\alpha}{\rightarrow} Y \overset{-\beta}{\rightarrow}Z \overset{-\beta}{\rightarrow}L \overset{-n\alpha}{\rightarrow} _{84}M^{218}$ the value of ‘n’ will be:

(a) 3
(b) 4
(c) 5
(d) 6

199. The Ra and U atoms in a sample of U-mineral are in the ratio of $1 : 2.8 \times 10^6$ . If $t_{1/2}$ period of Ra is 1620 years. The $t_{1/2}$ of U will be:

(a) $45.3 \times 10^9 years$
(b) $45.3 \times 10^{10} years$
(c) $4.53 \times 10^9 years$
(d) $4.53 \times 10^{10} years$

200. To start a nuclear fusion reaction, the temperature required is of the order of:

(a) $10^2K$
(b) $> 10^6K$
(c) $10^4K$
(d) $10^3K$

201. The ratio of specific charge of a proton and an $\alpha$ -particle is:

(a) 2 : 1
(b) 1 : 2
(c) 1 : 4
(d) 1 : 1

202. A piece of wood was found to have $C^{14} / C^{12}$ ratio 0.7 time that in a living plant. The time period when the plant died in $(t_{1/2} \text{of} C^{14} = 5760 \text{years})$ .

(a) 2770 years
(b) 2966 years
(c) 2980 years
(d) 3070 years

203. The half-life of a radioactive isotope is 3 hours. If the initial mass of the isotope was 300 g, the mass which remains undecayed in 18 hours would be:

(a) 4.69 g
(b) 2.34 g
(c) 1.17 g
(d) 9.36 g

204. If a $^aX_b$ species emits firstly a positron, then $2 \alpha \text{and} 2 \beta$ particles and in the last $1 \alpha$ particle is also emitted and finally converts to $^cY_d$ species, the correct relation is:

(a) a = c + 12, d = b – 6
(b) a = c – 8, d = b – 1
(c) A = c – 6, d = b – 0
(d) A = c – 4, a = b – 2

205. A human body requires the $0.01 \mu$ activity of radioactive substance after 24 hours. Half life of radioactive substance is 6 hours. Then injection of maximum activity of a radioactive substance that can be injected is:

(a) 0.08
(b) 0.04
(c) 0.16
(d) 0.32

206. The radioisotope, tritium $(^3_1H)$ has a half life of 12.3 years. If the initial amount of tritium is 32 mg, how many milligrams of it would remain after 49.2 years?

(a) 4 mg
(b) 8 mg
(c) 1 mg
(d) 2 mg

207. The radioactive isotope $^{60}Co_{27}$ which is used in the treatment of cancer can be made by (n, p) reaction. For this reaction the target nucleus is:

(a) $^{59}Ni_{28}$
(b) $^{59}Co_{27}$
(c) $^{60}Ni_{28}$
(d) $^{60}Ni_{27}$

208. The element used for carrying out the nuclear reaction is:

(a) Thorium-232
(b) Uranium-238
(c) Plutonium-239
(d) Neptunium-293

209. In nuclear reactor the control rods are made of cadmium because cadmium :

(a) Absorbs excess neutrons
(b) Absorb excess electrons
(c) Emits neutrons
(d) Emits electrons

210. The disintegration constant of a radioactive isotope whose half-life is 3 hours is:

(a) 1.57 per hour
(b) 1.92 per hour
(c) 1.04 per hour
(d) 0.231 per hour

211. The half life of a radioactive element is 40 days. Calculate the average life:

(a) 5.76 days
(b) 57.6 days
(c) 646 days
(d) 4.56 days

212. The number of $\alpha \text{and} \beta$ -particles emitted in the nuclear reaction $^{228}Th_{90} \to ^{212}Bi_{83}$ are:

(a) $4 \alpha \, \text{and}1 \beta$
(b) $3 \alpha \, \text{and} 7 \beta$
(c) $8 \alpha \, \text{and}1 \beta$
(d) $4 \alpha \, \text{and} 7 \beta$

213. India conducted an underground nuclear test at:

(a) Narora
(b) Tarapur
(c) Puskhar
(d) Pokhran

214. $^{232}Th_{90} \to ^{208}Pb_{82}$

The number of $\alpha \text{and} \beta$ -particles emitted during the above reaction is:
(a) $8\alpha \, \text{and} 4\beta$
(b) $8\alpha \, \text{and} 16\beta$
(c) $4\alpha \, \text{and} 2\beta$
(d) $6\alpha \, \text{and} 4\beta$

215. The half life period of radium is 1580 years. It remains 1/16 after:
(a) 1580 years
(b) 3160 years
(c) 4740 years
(d) 6320 years

216. Atom bomb is based on the principle of:

(a) Nuclear fusion
(b) Nuclear fission
(c) Nuclear transformation
(d) Carbon dating

217. The moderator used in nuclear reactor is:

(a) TEL
(b) $D_2O$
(c) $H_2O_2$
(d) R – O – R

218. Cadmium rods are used for which purpose?

(a) To emit electrons
(b) To absorb neutrons
(c) To emit neutrons
(d) To absorb electrons

219. Consider the following nuclear reactions:
$_{92}M^{238}\to _Yn^x + 2 _2He^4; _yN^x \to _BL^A + 2\beta^+$ the number of neutrons in the element L is:

(a) 142
(b) 144
(c) 140
(d) 146

220. The half-life of a radioisotope is four hours. If the initial mass of the isotope was 200 g, the mass remaining after 24 hours undecayed is:

(a) 1.042 g
(b) 2.084 g
(c) 3.125 g
(d) 4.167 g

221. The half-life of a radioactive isotope is three hours. If the initial mass of a the isotope were 256 g, the mass of it remaining undecayed after 18 hours would be:

(a) 4.0 g
(b) 8.0 g
(c) 12.0 g
(d) 16.0 g

222. The half-life of a substance A following first order kinetics is 5 days. Starting with 100 g of A, amount left after 15 days would be:

(a) 25 g
(b) 50 g
(c) 12.5 g
(d) 6.25 g

223. $\beta$ -particle is emitted in a radioactive reaction when:

(a) A proton changes to neutron
(b) A neutron changes to proton
(c) A neutron changes to electron
(d) An electron changes to neutron

224. $Na^{23}$ is the more stable isotope of Na. find out the process by which ${11}Na^{24}$ can undergo radioactive decay:

(a) $\beta^-$ emission
(b) $\alpha$ emission
(c) $\beta^+$ emission
(d) K electron capture

225. The number of neutrons accompanying the formation of $_{54}Xe^{139} \text{and} _{38}Sr^{94}$ from the absorption of slow neutrons by $_{92}U^{235}$ followed by nuclear fission is:

(a) 0
(b) 2
(c) 1
(d) 3

226. Loss of a $\beta$ -particle is equivalent to:

(a) Increase of one proton only
(b) Decrease of one neutron only
(c) Both (a) and (b)
(d) None of these

227. Decrease in atomic number is observed during:

(i) $\alpha$ emission
(ii) $\beta$ emission
(iii) Positron
(iv) Electron capture
(a) 1, 2. 3
(b) 2, 3, 4
(c) 1, 2, 4
(d) 1, 2, 3, 4

228. A sample of $^{238}U (t_{1/2} = 4.5 \times 10^9$ years) ore is found to contain $23.8 g ^{238}U \text{and} 20.6 g \text{of} ^{206}Pb$ . Calculate the age of the ore:

(a) $4.9 \times 10^6 \text{years}$
(b) $9.0 \times 10^{11} \text{years}$
(c) $9.4 \times 10^9 \text{years}$
(d) $4.5 \times 10^9 \text{years}$

229. $^{238}_{92}U \text{emits} 8 \alpha$ -particles and $6 \beta$ particles. The n / p ratio in the product nucleus is:

(a) 62/41
(b) 60/41
(c) 61/40
(d) 62/41

230. Which of the following cannot be accelerated:

(a) $\alpha$
(b) $\beta$
(c) P
(d) N

231. A radioactive isotope has a half life of 10 days. If today 125 mg is left over what was its original weight 40 days earlier:

(a) 2 gm
(b) 600 gm
(c) 1.5 gm
(d) 1 gm

232. A nuclide of an alkaline earth metal undergoes radioactive decay by emission of the $\alpha$ -particles in succession. The group of the periodic table to which the resulting daughter element would belong to:

(a) Gp.14
(b) GP.6
(c) GP.4
(d) GP.16

233. If a substance with a half life of 3 days is taken at other place in 12 days. What is the amount of substance left now:

(a) $\dfrac{1}{8}$

(b) $\dfrac{1}{4}$

(d) $\dfrac{1}{32}$

234. The element $^{232}_{90}Th$ belongs to 4n series which will be the end product of this series:

(a) $^{209}_{83}Bi$

(b) $^{208}_{82}P6$

(d) $^{207}_{82}Pb$

235. A photon of hard gamma radiation knocks a proton out of $^{24}_{12}Mg$ nucleus to form:

(a) Isotope of parent nucleus
(b) Isobar of parent nucleus
(c) The nuclide of $^{23}_{11}Na$
(d) The isobar of $^{23}_{11}Na$
236. Find the mass loss in the following $^2_1H + ^2_1H \to ^4_2He + ^1_0n$
[Here masses are as follows $_1^2H = 2.014, ^3_1H = 3.016; ^4_2He = 4.004 n = 1.008$ ]

(a) 0.018 a.m.u.
(b) 0.18 a.m.u.
(c) 0.0018 a.m.u.
(d) 1.8 a.m.u.

237. $t_{1/2} \text{of} ^{14}C$ is 5770 years, find time after which 72% of isotope left:

(a) 2742 years
(b) 2640 years
(c) 2880 years
(d) 280 years

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