Untitled Document

Question Bank No: 1

1. The half life of radium is 1600 years. The fraction of a sample of radium that would remain after 6400 years

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

2. In fusion the percentage of mass converted into energy is about

a)		0.01%
b)		0.1%
c)		1%
d)		10%

3. A positron has same mass as

a)		Proton
b)		$\propto$ - particle
c)		neutron
d)		electron

4. If the shortest wavelength in the lyman series is 911.6 $A^{0}$ , the longest wavelength in the same series will be

a)		1600 $A^{0}$
b)		2430 $A^{0}$
c)		1215 $A^{0}$
d)		$\propto$

5. Hydrogen atom are excited from grand state of the principal quantum number 4. Then the number of spectral lines observed will be.

a)		3
b)		6
c)		5
d)		2

6. Half life of a radioactive substance is 20 minutes. How much is the time interval between 33% decay and 67% decay?

a)		20 minutes
b)		25 minutes
c)		30 minutes
d)		40 minutes

7. Boron rods in nuclear reactor are used as a

a)		moderator
b)		control rods
c)		coolants
d)		protective shield

8. Penetrating power of x-rays depends on

a)		current flowing in the filament
b)		applied potential difference
c)		name of the target
d)		all of the above

9. The difference in angular momentum associated with the electron in the two consecutive orbits of hydrogen atom is

a)		(n-1) h / 2 $π$
b)		h / 2 $π$
c)		h / $π$
d)		h / 2

10. The frequency of $K_{α}$ line for gold atoms for gold is 79) is

a)		3 $\times$ $10^{10}$ Hz
b)		6 $\times$ $10^{19}$ Hz
c)		1.5 $\times$ $10^{19}$ Hz
d)		3 $\times$ $10^{19}$ Hz

11. A radioactive nucleus undergoes a series of decay as shown
$\overset{α}{A \to}$ $A_{1} \overset{β}{\to} A_{2} \overset{α}{\to} A_{3} \overset{γ}{\to} A_{4}$ .
If the mass number and atomic number of A are 180 and 72 respectively, then these numbers for $A_{4}$ are

a)		174, 71
b)		180, 70
c)		172, 69
d)		170, 69

12. Transitions from the state n=4 to n=3 in a hydrogen like atom results in ultraviolet radiations. Infrared radiations will be obtained in the transition

a)		5 to 4
b)		4 to 2
c)		3 to 2
d)		2 to 1

13. Binding energy per nucleon for $O^{16}$ is 7.99 MeV and it is 7.95 MeV for $O^{17}$ . Energy required to remove one neutron from $O^{17}$ is

a)		15.94 MeV
b)		0.04 MeV
c)		7.31 MeV
d)		0.06 MeV

14. When potential difference of 42,000 volts is used in x-rays tube to accelerate electrons. Then the x-ray radiation produced of maximum frequency is

a)		$10^{18}$ Hz
b)		$10^{19}$ Hz
c)		$10^{20}$ Hz
d)		$10^{6}$ Hz

15. If the radius of second stationary orbit of electron is Bohr's atoms is R then radius of third orbit will be

a)		R / 3
b)		9R
c)		2.25R
d)		3R

16. By emitting an $α$ particle Rn decays into Po with half life of 4 days. A sample contains 6.4 $\times$ $10^{10}$ atoms of Rn. After 12 days, the number of atoms left in the sample are

a)		2.1 $\times$ $10^{10}$
b)		0.8 $\times$ $10^{10}$
c)		3.2 $\times$ $10^{10}$
d)		0.53 $\times$ $10^{10}$

17. If the wavelength of K $α -$ line in copper is 1.54, then ionization energy of k electron in copper is

a)		10 $\times$ $10^{- 16}$ J
b)		17 $\times$ $10^{- 16}$ J
c)		12.9 $\times$ $10^{- 16}$ J
d)		11.2 $\times$ $10^{- 17}$ J

18. In a nuclear reaction, there is conservation of

a)		mass only
b)		energy only
c)		momentum only
d)		mass, energy and momentum

19. Thermal neutron has average K.E. of the order of

a)		0.003 Ke V
b)		0.03 Ke V
c)		3.0 Ke V
d)		0.3 e V

20. The electron emitted in $β$ radiation originates from

a)		inner orbits of atoms
b)		free electrons existing in nucleus
c)		decay of a neutron in a nucleus
d)		photo escaping from the nucleus

21. Liquid drop model of the nucleus was given by

a)		Chadwick
b)		Thomson
c)		Fermi
d)		Bohr

22. The electron has energy $- 13.6 eV$ in the lowest (n =1) orbit in hydrogen atom. Energy required to ionize a hydrogen atom which is in the first excited level

a)		1.9 eV
b)		10.2 eV
c)		13.6eV
d)		3.4 ev

23. Which of the following transitions gives an absorption line of least frequency

a)		n = 8 to n = 3
b)		n = 2 to n = 1
c)		n = 1 to n = 2
d)		n = 3 to n = 8

24. Atomic weight of Boron is 10.81 and it has two isotopes ${{}_{5}B}^{10}$ and ${{}_{5}B}^{11}$ . Then the ratio ${{}_{5}B}^{10}$ and ${{}_{5}B}^{11}$ in nature woul be

a)		15 : 16
b)		81 : 12
c)		19 : 81
d)		10 : 11

25. If the decay constant of ${}_{80}{PO}^{206}$ is $λ$ then its half life and mean life are

a)		$\frac{1}{λ}$ and $\frac{\log_{e} 2}{λ}$ respectively
b)		$\frac{1}{λ}$ and $\frac{λ}{\log_{e} 2}$ respectively
c)		$\frac{\log_{e} 2}{λ}$ and $\frac{1}{λ}$ respectively
d)		$\frac{1}{λ}$ and $\frac{2}{\log_{e} λ}$ respectively

26. Which one of the following processes is not related to radioactive disintegration ?

a)		Positron emission
b)		Electron capture
c)		$α -$ decay
d)		Nuclear fusion

27. If ionization energy of the hydrogen atom is 13.6 eV, then the wavelength of the first line of Lyman series

a)		12.20 $\overset{\circ}{A}$
b)		1.22 $\overset{\circ}{A}$
c)		122 $\overset{\circ}{A}$
d)		1216 $\overset{\circ}{A}$

28. Energy released in the fission of ${}_{92}{U^{235}}$ nucleus is 200 MeV. If a reactor fuel is ${}_{92}{U^{235}}$ and operating at power level 5 then fission rate will be about

a)		1.5 $\times 10^{16} \sec^{- 1}$
b)		1.5 $\times 10^{17} \sec^{- 1}$
c)		1.5 $\times 10^{10} \sec^{- 1}$
d)		1.5 $\times 10^{11} \sec^{- 1}$

29. Half lives of two radio active substances are 40 and 20 minutes respectively and initially samples were having equal number of nuclei. After 80 minutes ratio of the remaining numbers of nuclei will be

a)		4 : 1
b)		1 : 16
c)		8 : 1
d)		16 : 1

30. In the second orbit of hydrogen atom, angular momentum for an electron as per Bohr's model of atom will be

a)		$π / h$
b)		2 $π h$
c)		h/ $π$
d)		2h/ $π$

31. The ratio of minimum to maximum wave length in Balmer series is

a)		3 : 4
b)		1 : 4
c)		5 : 36
d)		5 : 6

32. If the magnitude of charge of proton and electron in a hydrogen atom were doubled, the energy emitted in the transition from n = 2 to n = 1 would change by a factor of

a)		8
b)		4
c)		1/4
d)		16

33. The ratio of the areas of the circular orbits of an electron for the first excited state in a hydrogen atom to that for the ground state is

a)		4 : 1
b)		16 : 1
c)		2 : 1
d)		3 : 1

34. The energy difference between the firt two levels of hydrogen atom is 10.2 eV. For another element of mass number 20 and atomic number 10, it will be

a)		0.102 eV
b)		0.51 eV
c)		2040 ev
d)		1020 eV

35. Solar energy is mainly due to

a)		fusion reaction
b)		fission reaction
c)		combustion reaction
d)		chemical reaction

36. The nucleus ${Cd}_{49}^{115}$ after two successive $β$ - decays will give

a)		${Pa}_{46}^{115}$
b)		${In}_{49}^{114}$
c)		${Sn}_{50}^{113}$
d)		${Sn}_{50}^{115}$

37. Complete the equation for the following fission process $U_{92}^{235} + n_{0}^{1} \to {Sr}_{35}^{90} + ...$

a)		${Xe}_{54}^{146}$
b)		${Xe}_{54}^{145}$
c)		${Xe}_{54}^{143} + {3 n}_{0}^{1}$
d)		${Xe}_{54}^{42} + n_{0}^{1}$

38. In case of an artificial radio active tranformation as given by $P_{15}^{30} \to {Si}_{14}^{30} + X$ , the emitted particle X is

a)		neutron
b)		proton
c)		positron
d)		electron

39. Energy released in the fission of a single $U^{235}$ nucleus is 200 MeV. The fission rate of a $U^{235}$ fuelled reactor operating at a power level of 5W is

a)		${1.56 \times 10}^{16} s^{- 1}$
b)		$1.56 \times 10^{11} s^{- 1}$
c)		$1.56 \times 10^{6} s^{- 1}$
d)		$1.56 \times$ $10^{17} s^{- 1}$

40. The critical mass of a fission reaction is

a)		the mass to start a nuclear fission reaction
b)		the minimum mass for the chain reaction
c)		the size of the reactor core
d)		the size of the fuel +size of the moderator

41. In a nuclear reaction $C_{6}^{11} \to B_{5}^{11} + β^{+} + X$ , X stands for

a)		an electron
b)		a proton
c)		a neutron
d)		a neutrino

42. When deuterium is bombarded on an $O_{8}^{16}$ nucleus , an $α$ - particle is emitted. Then the product nucleus is

a)		$N_{7}^{13}$
b)		$S_{5}^{10}$
c)		${Be}_{4}^{9}$
d)		$N_{7}^{14}$

43. Two radioactive samples prepared 12 years ago have half lives 3 years and 4 years respectively. Both samples have the same activity C today. The difference between the activities 12 years ago when the samples were fresh was

a)		8C
b)		12C
c)		4C
d)		0.75C

44. A parcel of radioactive sample is being prepared in the laboratory for despatch to customer by ship. It is required that the sample should have active 20mCi after six months. If the half life of the sample is 4months, the minimum activity that the sample should have when packed is

a)		98.6mCi
b)		44mCi
c)		78.4mCi
d)		56.6mCi

45. A freshly prepaired radioactive source of half life 2 hours emits radiation of intensity which is 64 times the permissible safe level. The minimum time after which it would be possible to work sefely with the source is

a)		6hr
b)		12 hr
c)		18hr
d)		24hr

46. A rate meter measures the number of disintegration per sounds from a radioactive source. It gives a count of 320 per second. Ninety minutes later it gives only 40 counts per second. The half life of the source is

a)		45 min
b)		60 min
c)		30 min
d)		75 min

47. The radioisotope used to study thyroid gland is

a)		carbon
b)		cobalt
c)		iron
d)		iodine

48. The nucleus $C_{6}^{12}$ absorbs an energetic neutron and emits a $β$ - particle. The resulting nucleus is

a)		$N_{7}^{14}$
b)		$N_{7}^{13}$
c)		$B_{5}^{13}$
d)		$C_{6}^{13}$

49. If the decay constant of a radioactive substance is $λ$ , then its half life and mean life are respectively

a)		$\frac{1}{λ}$ and $\frac{\log_{e} 2}{λ}$
b)		$\frac{\log_{e} 2}{λ}$ and $1 / λ$
c)		$\frac{\log_{10} 2}{λ}$ and $λ$
d)		$\frac{\log_{10} 2}{λ}$ and $\frac{1}{λ}$

50. In which of the radioactive disintegration a neutron is dissociated into a proton and an electron?

a)		$H^{+ +}$ emission
b)		$β$ - emission
c)		$γ$ - emission
d)		positron emission