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ECAT Physics Nuclear Physics Test Online

Danial MalikLast Updated: April 18, 2025

Nuclear Physics Online Test

ECAT Nuclear Physics Chapter Online Test

Total Questions:	179
Time Allowed:	80 Minutes
Total Marks:	179
How to Attempt Test:	Please choose the right Option in MCQ-type question.
Test Helpful For:	ECAT Entry Test Physics Online Test Interview Questions about Physics All Universities Entrance Test Recruitments Tests

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1. Neutron and proton are commonly known as

Nucleon

Meson

Boson

Quartz

2. Electrons

Can exist inside the nucleus

Cannot exist inside the nucleus

Can exist both inside and outside the nucleus

Do not know

3. Transuranic elements have atomic number

Greater than 72

Greater than 82

Greater than 92

Greater than 102

4. Nuclear forces exist between

Proton-proton

Proton-neutron

Neutron-neutron

All of these

5. A particle having the mass of an electron and the charge of a proton is called a

Antiproton

Positron

Gamma rays

Photon

6. Alpha radiation are advised for the treatment of skin of a patient because

They are positively charger

They are helium nuclei

They are highly ionizing

They are less penetration

7. Beta particle has penetration power

100 times more than that of an alpha particle

100 times has than that of an alpha particle

10 times more than that of an alpha particle

1000 times less than of an a- particle

8. An alpha particle has a charge of:

+2e

-2e

-e

9. Alpha particles are highly ionizing due to

Their greater density

Their high charge and low speed

Their greater energy

Their greater mass

10. Beta particles are much less ionizing than alpha particles because of

Their smaller charge and large speeds

Their smaller mass

Their smaller energy

They’re coming out of the nuclei

11. beta-Particles possess greater penetration power than that of alpha – particles due to its

Greater ionization power

Smaller ionization power

Neither greater now smaller ionization power

The same ionization power

12. Alpha particles are highly ionizing because of:

Their high charge and low speeds

Their greater mass

Their larger energy

Their constituents

13. Which one of the following radiation is extremely penetrating?

Neutrons

Alpha rays

Beta rays

Gamma rays

14. Out of 10 mg of a radio active sample, 1.25 mg remains undecayed after 6 hours. The mean life of the sample in hours is

0.693

2/0.693

4/0.693

0.693/4

15. Half life of radium is 1590 years. In how many years shall the earth loss all its radium due to radioactive decay?

1590 x 10⁶ years

1590 x 10¹² years

1590 x 10²⁴ years

Never

16. Mass defect per nucleon is

Binding energy of nucleus

Packing fraction

Average energy of nucleus

All of above are one and same thing

17. Average energy required to remove one nucleon from the nucleus is called

Binding energy per nucleon

Energy of decay

Destruction energy

All of these

18. The half lives of radioactive elements X and Y 3 minutes and 27 minutes respectively. If the activities of both are same, then the ratio of number of atoms of X and Y will be

1:9

1:10

1:1

9:1

19. Draw-back of Geiger counter is

Very high voltage

Slow counting

Both A and B

None of these

20. Geiger counter is suitable

For slows counting

For fast counting

For extremely fast counting

For fast and slow counting

21. A Geiger counter counts radioactive particles by

Collecting and measuring the charges of the particles

Under going a chemical reaction with each incident, particle

Amplifying the sound theory make as theory strike the walls of tube

Emitting detectable light pulses when struck

22. A device that may be used to detect the passage of a single, light energy charged particle is called a

Dosimeter

Mass spectro graph

Geiger counter

Wilson’s cloud Chamber

23. A solid state detector mainly consists of a

Silicon diode

Germanium Crystal

Silicon crystal

Transistor

24. During fusion of hydrogen into helium

Energy is absorbed

Energy is released

Mass is increased due to energy absorption

Mass is reduced due to energy released

25. For chain reaction to build up the size of the radioactive target should be

greater than the critical size

less than the critical size

equal to the critical size

all of above can build up a change reaction

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26. Mass defect per nucleon is

Binding energy of nucleus

Packing fraction

Average energy of nucleus

All of above are one and sane thing

27. Tick the correct statement

Moderators slow down the neutrons

Moderators bring the neutrons to rest

Moderators absorb the neutrons

Moderators reflect the neutrons

28. Fission chain reaction in a nuclear reactor can be controlled by introducing

Iron rods

Graphite rods

Cadmium rods

Platinum rods

29. During fission process a large amount of

Heat energy is released

Nuclear energy is released

Chemical energy is released

Light energy is released

30. If one or more of the neutrons emitted during fission can be used to build up further fission then the reaction is self sustained and is known as

Fission reaction

Fusion reaction

Chain reaction

Chemical reaction

31. Neutron was discovered in 1932 by

Bohr

Chadwick

Dirac

Fermi

32. How many times the radius of the atom is larger than the radius of the nucleus

10³

10⁵

10⁷

None of these

33. The total charge of any nucleus is

None of these

34. The de Broglie wave corresponding to a particle of mass m and velocity v has a wavelength associated with it

h/mv

hm v

mh/v

m/hv

35. A mass spectrograph is the device which is use to

Separate isotopes

Find the isotopes

Find the neutrons

A and B

36. The mass density of a nucleus varies with mass number A as

A²

Constant

1/A

37. The most abundant isotope of neon is

Neon-20

Neon-21

Neon-22

Neon-23

38. For the structural analysis of crystals, X-rays are used because

X-rays have wavelength of the order of the inter-atomic spacing

X-rays are highly penetrating radiations

Wavelength of X-rays is of the order of nuclear size

X-rays are coherent radiations

39. How many types of radiations are radiated from a radioactive elements?

α, β

α, β, ϒ

40. Mass defect of an atom refers to

Inaccurate measurement of mass of nucleons

Mass annihilated to produce energy to bind the nucleus

Packing fraction

Difference in number of neutrons and protons in the nucleus

41. Marie curie and Pierre Curie discovered two radioactive elements which are

Uranium and Polonium

Polonium and Radium

Radium and uranium

Uranium and Plutonium

42. Which of the following undergo fission reaction easily by slow moving neutrons?

U-235, P-239

P-239, Th-234

U-238, Rn-232

Th-234, U-228

43. Radioactivity is purely a nuclear phenomenon, and is not affected by

Physical or chemical reaction

Temperature

Pressure

All of these

44. A radioactive reaction is ₉₂U²³⁸ →₈₂Pb²⁰⁶. How many α and β particles are emitted?

10α, 6β

4 protons, 8 neutrons

6 electrons, 8 protons

6β, 8α

45. When an α -particle emitted, the change in the nucleus is

“A” decreases 4 “Z” decreases 3

“A” decreases 4 “Z” decreases 2

“A” decreases 4 Z decreases 2

None of these

46. The number of atoms decaying in a particular period is proportional to

Atoms present

Atoms decayed

Atoms after decayed

None of these

47. The half-life of iodine -131 is

2 days

4 days

8 days

10 days

48. Ionization of matter, when α –particle pass through it is by

Direct elastic collision

Electrostatic attraction

Inelastic collision

A and B

49. A nucleus nXᵐ emits one α and β-particles. The resulting nucleus is

50. The rate of disintegration of an isotope is 10¹⁷ atoms/second and half-life is 1445 years. Then number of atoms of the starting sample of the element is

1.44 x 10¹⁷

1.4 x 10¹⁷

6.57 x 10²⁷

None of these

Page 3 of 8

51. The time taken by the entire electron pulse to reach anode, in Geiger Muller tube is

1 ms

Less than 1 μs

More than 1 μs

None of these

52. The dead time of the Geiger Muller counter is

~ 10¯⁴ sec

~ 10¯⁵ sec

~ 10¯⁶ sec

None of these

53. The principle gas filled with the small amount of gas in a Geiger Muller tube is

More than 50%

More than 70%

More than 80%

More than 35%

54. The quenching of gas by a quenching gas is called

Quenching

Self quenching

Forced quenching

None of these

55. Geiger Muller counter can be used to determine the

Range of ionizing particle

Mass of ionizing particle

Charge of ionizing particle

None of these

56. Solid state detectors are

Accurate

More efficient

Fast enough

All of these

57. In the breakage of ²³⁵₉₂U the average neutron emitted are

Two neutron

2.5 neutron

Three neutron

None of these

58. The average binding energy of a nucleon inside an atomic nucleus is about

8 MeV

8 eV

8 joules

8 ergs

59. The mass density of a nucleus varies with mass number A as

A²

Constant

1/A

60. Curie is a unit of

Energy of gamma-rays

Half-life

Radioactivity

Intensity of gamma-rays

61. The energy released in a typical nuclear fusion reaction is approximately

25 MeV

200 MeV

800 MeV

1050 MeV

62. The binding energy per nucleon is of maximum value in case of

⁴₂He

⁵⁶₂₆Fe

¹⁴¹₅₆Ba

²³⁵₉₂U

63. Mass defect of an atom refers to

Inaccurate measurement of mass of nucleons

Mass anihilinated to produce energy to bind the nucleus

Packing fraction

Difference in number of neutrons and protons in the nucleus

64. Which of the following undergo fission reaction easily by slow moving neutrons?

U-235, P-239

P-239, Th-234

U-238, Rn-232

Th-234, U-238

65. The element used for radioactive Carbon dating for more than 5600 years is

C-14

U-234

U-238

Po-94

66. The penetrating power of X-rays can be increased by

Increasing the current in the filament

Decreasing the current in the filament

Increasing the potential difference between the cathode and the anode

Decreasing the potential difference between the cathode and anode

67. The frequencies of X-rays, ϒ-rays and ultraviolet rays are respectively a, b and c. Then

a > b, b > c

a < b, b < c

a < b, b > c

a > b, b < c

68. Einstein’s work on the photoelectric effect provided support for the equation

E = mc²

E = hw

E = - Rhc/n²

K.E. = ½ mv²

69. The radius of Bohr’s first orbit is r. What is the radius of the first orbit in the singly ionized helium atom?

r/2

r/4

70. The wavelength of the first line of Balmer series of hydrogen atom is λ. What will be the wavelength of the same line in doubly ionized lithium?

λ/2

λ/9

λ/8

λ/27

71. At a specific instant emission of radioactive compound is deflected in a magnetic field. The compound can emit
(i) Electrons
(ii) Protons
(iii) He²⁺
(iv) Neutrons
The emission at the instant can be

i, ii, iii

i, ii, iii, iv

ii, iii

72.

β-emission

α-emission

e¯ capture

fission

73. In photoelectric emission, the intensity of light is reduced, then the stopping potential

Would decrease

Would increase

Would remain the same

My increase or decrease depending on the polarization of light

74. An X-ray (gamma ray) is

An energetic neutron emitted by a nucleus

An energetic electron emitted by a nucleus

An energetic photon emitted by a nucleus

An energetic proton emitted by a nucleus

75. The number of electrons ejected from photosensitive surface depends upon

The intensity of incident light

The frequency of light

The wavelength of light

None of these

Page 4 of 8

76. The minimum energy in electron volt required to strip off ten times ionized sodium atom (i.e. Z – 11) of its last electron is

13.6 MeV

13.6 x 11 eV

13.6 x 11² eV

13.6 x 11³ eV

77. The orbital electron of the hydrogen atom jumps from the ground state to a higher energy state and its orbital velocity is reduced to one third of its initial value. If the radius of the orbit in the ground state is r, then what is the radius of the new orbit?

78. After five half-lives what will be the fraction of initial substance

(½)¹⁰

(½)⁵

(½)⁴

(½)³

79. A radioactive nucleus emits a beta particle. The parent and daughter nuclei are

Isotopes

Isotones

Isomers

Isobars

80. Which one of the following is not possible?

₇N¹⁴ + ₀n¹ → ₇N¹⁶ + ₁H¹

₁₆N³² + ₁H¹ → ₁₇CI³⁵ + ₂He⁴

₈O¹⁶ + ₀n¹ → ₇N¹⁴ +3 ₁H¹ + 2 ₋₁β⁰

₁H¹ + ₁H¹ → ₂He⁴

81. A source of light is placed at a distance of 1m from a photocell and the cut off potential is found to be V₀. If the lamp is now placed at a distance of 2 m, the cut off potential will become

2 V₀

V₀/2

V₀/4

V₀

82. The threshold frequency of the photoelectrons is v₀. The light is at frequency v. Then which of the following is correct for the emission to take place?

v = v₀

v = 2 v₀

v < v₀

v > v₀

83. Photoelectrons are emitted with a maximum speed of 7 x 10⁵/s from a surface when light of frequency 8 x 10¹⁴ Hz is showered on it, the threshold frequency for this surface is

2.32 x 10¹⁴ Hz

4.64 x 10¹⁴ Hz

4.64 x 10¹⁶ Hz

4.64 x 10¹⁸ Hz

84. The most important characteristics of electron is the production of X-rays is

Charge of electron

Mass of electrons

Revolution of electron around the nucleus

Speed of electrons

85. Rate of photoelectric emission is proportional to

Intensity of incident radiations

Frequency of incident radiations

Square of intensity of incident radiations

Square of the frequency of incident radiations

86. For photoelectric emission to take place

Frequency of incident radiation should be less than threshold frequency

Frequency of incident radiation may have any value

Weave length of incident radiation should be less than threshold wavelength

Wavelength of incident radiation may have any value

87. In photoelectric emission the number of photoelectrons emitted per second depends on

Wavelength of incident light

Frequency of incident light

Intensity of incident light

All of these

88. Which one among the following shows particle nature of light?

Photo-electric effect

Interference

Refraction

Polarization

89. The potential energy of the orbital electron in the ground state of hydrogen atom is E. What is its kinetic energy?

E/4

E/2

2 E

4 E

90. The orbital radius of the electron in the hydrogen atom changes from r to 4r. The energy of the orbital electro will change from E to:

4 E

2 E

E/2

E/4

91. Source of Sun’s energy is

Burning of hydrogen

Fission reactions involving hydrogen

Fusion reaction involving hydrogen

Some other source

92. In the disintegration series

the value of Z and A respectively will be

92, 236

88, 230

90, 234

91, 234

93. The decay constant of a radioactive element is 1.5 x 10¯⁹ per second. Its mean life in seconds will be

1.5 x 10⁹

4.62 x 10⁸

6.67 x 10⁸

10.35 x 10⁸

94. Sodium and copper have work functions 2.3 eV and 4.5 eV respectively. Then the ratio of the wavelengths is nearest to

1 : 2

4 : 1

2 : 1

1 : 4

95. When X-rays pass through s strong uniform magnetic field, then they

Do not get deflected at all

Get deflected in the direction of the filed

Get deflected in the direction opposite to the filed

Get deflected in the direction perpendicular to the field

96. Photons of 5.5 eV energy fall on the surface of the metal emitting photoelectrons of maximum kinetic energy 4.0 eV. The stopping voltage required for these electrons are

5.5 V

1.5 V

9.5 V

4.0 V

97. A deuteron has 1 proton and 1 neutron. If the mass of a proton be Np and that of a neutron be NN, then mass of one deuterium atom is

= Np + Nn

< Np + Nn

> Np + Nn

> or = Np + Nn

98. What is binding energy of hydrogen nucleus?

Zero

13.6 eV

More than 13.6 eV

Infinite

99. What determines half-life of a radioactive element?

Atomic number

Mass number

Temperature

None of these

100. The ionization potential of a hydrogen atom is 13.6 V. What twill be the energy of the electron in the second orbit?

– 10.2 eV

– 3.40 eV

– 1.51 eV

– 0.85 eV

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101. The total energy of an electron in the excited state corresponding to n = 3 is E. What is its potential energy with proper sign?

– 2E

– E

102. Minimum energy required to take out the only one electron from ground state of He⁺ us

13.6 eV

54.4 eV

27.2 eV

6.8 eV

103. Photocells are used for the

Reproduction of films from the cinema files

Reproduction of sound from the cinema films

Automatic switching of street light

Both B and C

104. In radioactive decay, a β-particle is emitted. This happens because

A neutron is converted to proton and an electron is emitted

Valence electron is driven out of the outer shell

By product of transition of electron from inner to outer shell

By product of transition of electron from outer to inner shell

105. In a mean life of a radioactive sample

About 1/3 of substance disintegrates

About 90% of the substance disintegrates

About 2/3 of the substance disintegrates

Almost all the substance disintegrates

106. Which of the following processes will result into fission reaction?

₉₂U²³⁵ is bombarded with fast moving neutrons

₉₂U²³⁵ is bombarded with thermal neutron

U²³⁸ is bombarded with slow moving neutrons

U²³⁵ being unstable breaks into smaller fragment

107. The line spectrum is obtained when the incandescent vapours at low pressure of the excited substance are in:

Atomic state

Molecular state

Plasma state

Ionized state

108. The band spectrum is obtained whenever the incandescent vapour of the excited substance are in their

Atomic state

Molecular state

Plasma state

Ionized state

109. Photoelectric effect can be explained by assuming that light

Is a form of transverse wave

Is a form of longitudinal wave

Can be polarized

Consists of quanta

110. The work function of a metal is 2.8 eV. Its threshold wavelength will be

4400 Å

4433 Å

5434 Å

433 Å

111. The stopping potential depends on

Intensity of incident light

Frequency of incident light

Both A and B

Neither A not B

112. Photoelectric threshold wavelength for tungsten is 2300 Å. Work function for it will be

5.39 eV

53.9 eV

5.39 x 10¯⁸ e

None of these

113. Average binding energy per nucleon for a heavy nucleus is

8 x 10¯³ eV

0.5 eV

7.6 MeV

13.5 eV

114. The rate of disintegration is 10¹⁷ atoms/second and half-life is 1445 years. Then no. of atoms is

1.44 x 10¹⁷

1.4 x 10¹⁷

6.57 10²⁷

None of these

115. Nuclear fusion is the source of energy in

Nuclear reactor and sun

Sun and hydrogen bomb

Nuclear reactor and atom bomb

Sun and atom bomb

116. The total energy of an electron in a exited state is E. What is its kinetic energy with proper sign?

- 2 E

2 E

- E

117. The hydrogen atom in a sample is in the excited state corresponding to n = 3. How many spectral lines can be emitted?

118. For the given statements choose the correct answer
(i) The spectrum of α-emission radioactive decay is discrete
(ii) The spectrum of β-emission radioactive decay is discrete

a is true but b is false

b is true but a is false

b is true

a is true

119. A chain reaction is continuous due to

Large mass defect

Large energy

Production of more neutrons in fission

None of these

120. Nucleus of an atom whose atomic mass is 24 consists of

11 electrons, 11 protons and 13 neutrons

11 electrons, 13 protons and 11 neutrons

11 protons and 13 neutrons

11 protons and 13 electrons

121. A photoelectric cell is illuminated by a point source of light 1 m away. When the source is shifted to 2 m, then

Number of electrons emitted is half the initial number

Each emitted electron carries half the initial energy

Number of electrons emitted is a quarter of the initial number

Each emitted electron carries one quarter of the initial energy

122. The phenomenon inverse to photoelectric effect is

Compton effect

Raman effect

Pair production

Production of X-rays

123. Every motion is

Relative

Absolute

Zero

None of these

124. The transition of the electron takes place from n = 2 orbit to n = 1 orbit. Which of the following give the shortest wavelength?

Hydrogen atom

Deutrium atom

Single ionized helium

Doubly ionized helium

125. The ionization energy of hydrogen atom is 13.6 eV. The ionization energy of helium atom would be

1.6 eV

27.2 eV

6.8 eV

54.4 eV

Page 6 of 8

126. 1 gram of radioactive element reduces to 1/3 gram at the end of 2 days. Then the mass of the element remaining at the end of 6 days is (in gram):

1/9

1/6

1/27

1/12

127. Alpha-particles are

Protons

Positron

Neutrally charged

Ionized helium atoms

128. Which of the following statements is NOT correct?

The laws of physics are the same in all inertial frames

The speed of light in free space has the same value in all inertial frames

Two events which occur simultaneously in one reference frame also must appear to occur simultaneous in another reference frame

Einstein rejected Newton’s idea of absolute time

129. The simple assumption that all possible reference frames moving with uniform velocity relative to one another are equivalent for the statement of laws of physics is called the

Principle of Relativity

Uncertainty Principal

Pauli’s Exclusion Principle

None of these

130. Special theory of relativity states that

All laws of physics are the same in every inertial reference frame

Every motion is relative

Light has dual nature

Energy and mass are inter convertible

131. Special theory of relativity states that

Time is absolute

The speed of light in a vacuum, measured in all inertial reference frames always has the same value of c, no matter how fast the source of light and the observer are moving relative to each other

Space is absolute

At rest mass of an object is always zero

132. Which of the following is the property of Rydberg constant?

It is universal constant

It is same for all the hydrogen like atoms

It depends on the atomic number of the atom

It depends on the mass number of the atom

133. Complete the equation for the following fission process: ₅₄U²³⁵ + ₀n¹ → ₃₈Sr⁹⁰ + …………….

₅₄Xe¹⁴³ + 3 ₀n¹

₅₄Xe¹⁴⁵

₅₄Xe¹⁴²

₅₄Xe¹⁴² + ₀n¹

134. An artificial radioactive decay series begins with unstable ²⁴¹₉₄PU. The stable nuclide obtained after eight α-decays and five β-decays is

²⁰⁹₈₃Bi

²⁰⁹₈₂Pb

²⁰⁵₈₂T1

²⁰¹₈₂Hg

135. If the radioactive decay constant of radium is 1.07 x 10¯⁴ per year, then its half-life period is approx. equal to

8,900 years

7,000 years

6,476 years

2,520 years

136. The half-life (T) and the disintegration constant (λ) of a radioactive substance are related as

λT = 1

λT = 0.693

T/λ = 0.693

λ/T = 0.693

137. A nucleus nXᵐ emits one α and β-particles. The resulting nucleus is

nXᵐ¯⁴

₂₋n Yᵐ¯⁴

n₋₄ Zᵐ¯⁴

n₋₁ Zᵐ¯⁴

138. The mass of the particle moving with velocity of light is equal to what?

Zero

Infinite

Finite

Unit

139. Two photons are traveling is opposite directions with velocity c. What is the relative velocity of one with respect to the other?

Zero

1/√c

140. An observer measures the length of a space ship and finds that it is exactly one-third of its proper length. What is the speed of the space-ship relative to the observer?

2√2 C/3

2/3 c

√2/3 c

141. A rod has a proper (or rest) length L₀. The length of the same rod as measured by an observer moving with a velocity v relative to the rod, is give by

L = L₀ √1-(v/c)²

L₀ = L √1-(v/c)²

L = L₀ √1+(v/c)²

L = L₀ √1- v/c

142. A radioactive element ₉₀X²³⁸ decay into ₈₃Y²²². The no. of β particles emitted are

143. In Nuclear Fission 0.1% mass is converted into energy. The energy released by the fission of 1kg mass will be

9 x 10 ¹⁶ J

9 x 10 ¹⁹ J

9 x 10 ¹³ J

9 x 10 ¹⁷ J

144. A body of some material capable of absorbing all heat radiation incident on it and can emit in turn all the radiation at constant temperature after it is in equilibrium with it is called

Black body

Black body radiation

Black body cavity

Cavity radiation

145. Which theory explains that energy exchange takes place in discrete “bundles”?

Special theory of relativity

Quantum theory

Corpuscular theory

Bohr’s theory

146. If half-life of a radioactive atom is 2.3 days then its decay constant would be

0.1

0.2

0.3

2.3

147. In a nuclear reaction, which of the following is conserved?

Atomic number

Mass number

Atomic number, Mass number and Energy

None of these

148. Mathematically Quantum theory is stated as

E = mc²

E = hf

V = mλ

None of these

149. The rest mass of photon is

Finite

Zero

Infinite

Unit

150. The velocity of photon is

3 x 10⁸ ms¯¹

3 x 10⁸ cms¯¹

3 x 10⁸ cms¯²

3 x 10⁵ cms¯²

Page 7 of 8

151. Photoelectric effect is governed by the equation

E = mc²

V = nλ

E = hf

½ mv² max = hf - φ

152. Energy of 1 g uranium is equal to:

9.0 x 10¹³ J

9.0 x 10¹⁹ J

3.0 x 10¹⁶ J

3.0 x 10¹⁷ J

153. Which one is not emitted from radioactive substance?

Electron

Proton

Gamma rays

Helium nucleus

154. The amount of current produced by photoelectric effect depends upon

Frequency of incident light

Wavelength of incident radiation

Intensity of incident radiation

Speed of incident emitted from a metal surface

155. Einstein explained photoelectric effect on the basis of

Wave theory of light

Special theory of light

Quantum theory of light

All of these

156. The photoelectric effect establishes that

Light travels in the form of quanta of energy

Light travels in the form of transverse waves

Light travels in the form of longitudinal waves

Light is a transverse electromagnetic wave

157. At frequencies of the incident radiation above the threshold frequency, the photoelectric current in a photoelectric cell increases with increase in

Intensity of incident radiation

Wavelength of incident radiation

Frequency of incident radiation

Speed of incident emitted from a metal surface

158. For each material emission occurs only for certain definite frequency f₀ of light called

Hertz

Critical frequency

Threshold frequency

Minimum frequency

159. The amount of energy needed to remove electrons from the metal surface depends upon

Work

Work Function

Power

Wavelength

160. In case of photoelectric effect, amount of energy in each photon depends on the

Rest mass

Frequency of incident light

Momentum

Wavelength

161. If you are to choose a light from the given below, which one may be the most suitable for photoelectric effect?

Visible light

Ultra-violet light

Infra-red light

Far-infra light

162. An observer sitting in an airplane and moving with a very high speed observes a meter rod placed on ground. The rod appears to him

Equal to 100 cm

Less than 100 cm

Greater than 100 cm

None of these

163. Photoelectric Effect is a phenomenon in which electromagnetic waves exhibit

Wave nature

Particle nature

Wave & particle nature

None of these

164. What percentage of radioactive substance is left after 5 half-lives?

31%

3.125%

0.3%

165. ₁H¹ + ₁H¹ + ₁H² → X + ₋₁ e⁰ + Energy. The emitted particle is

Neutron

Proton

α-particle

Neutrino

166. A photocell is based on

Compton Effect

Photoelectrons

Photoelectric Effect

Pair Production

167. On moving from one place to another electromagnetic radiations behave as

Particles

Waves

Both particles and Waves

None of these

168. The materialization of energy takes place in which phenomenon?

Annihilation

Pair Production

Compton Effect

Photoelectric Effect

169. “The product of the uncertainties in momentum (∆p) and position (∆x) of particle at some instant is approximately f₀ the order of Planck’s constant h”. This is called

Pauli’s Exclusion Principle

Heisenberg Uncertainty

Photoelectric Effect

Compton Effect

170. The process of scattering of an x-ray photon by an electron is called

Compton Effect

Photoelectric Effect

Pair production

Annhilation

171. The initial nucleus of uranium series is ₉₂U²³⁸ and the final nucleus is ₈₂Pb²⁰⁶. When uranium decays to lead how many α and β particles are produced?

6, 8

8, 6

4, 3

3, 4

172. At any instant the ratio of the amount of radioactive substance is 2:1. If their half lives be respectively 12 and 16 hours, then after two days, what will be the ratio of the substances?

1 : 1

2 : 1

1 : 2

1 : 4

173. In Compton Effect

The scattered photon has frequency less than that of the incident photon

The scattered photon has frequency greater than that of the incident photon

The scattered photon has frequency equal to the incident photon

None of these

174. When we try to stop a very high photon it loses its identity and disintegrates into an electron and positron. This is called

Pair Production

Annihilation

X-rays Production

Compton Effect

175. A process reverse to the pair production is known as

Photoelectric Effect

Annihilation

X-rays Production

Compton Effect

Page 8 of 8

176. Joule Sec is the unit of

Heat

Wave energy

Energy

Plank’s Constant

177. Einstein’s theory of relativity suggests that

The laws of physics are the same in all inertial frames of reference

The speed of light in free space is universal constant

The speed of light is independent of the speed of the observer

All of these

178. An electric eye operates because of

The Compton effect

y-radiations

Photoelectric effect

Radiations pressure

179. A beam of monochromatic radiation falls on a metal and photoelectrons are emitted. The rate of emission of photoelectrons will be double if

A beam of double the intensity is used

Radiation of double the frequency is used

Radiation of double the wavelength is used

The temperature of the metal is doubled

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Danial MalikLast Updated: April 18, 2025

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