ECAT Physics Modern Physics Test Online

Maan AliLast Updated: April 18, 2025

Modern Physics MCQS Online Test

ECAT Modern Physics Chapter Online Test

Total Questions:	116
Time Allowed:	50 Minutes
Total Marks:	166
How to Attempt Test:	Please choose the right Option in MCQ-type question.
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Page 1 of 5

1. Mark the wrong statement:

A frame of reference which is either at rest or moves with a constant velocity is called an inertial frame of reference

An un-accelerated frame of reference is called an inertial frame of reference

All the frames of reference in uniform rectilinear motion are equivalent

Newton’s laws of motion are valid in an accelerated (non inertial) frame of reference

2. In translatory motion, the axes of the frame of reference of the object remains always parallel to the corresponding axes of?

Observer’s frame of reference

Mover’s frame of reference

Rotator’s frame of reference

None of these

3. Inertial frame of reference is that

Which has large inertia

Which has no inertia

In which Newton’s first law of motion is applicable

None of these

4. Special theory of relativity treats problems involving

Inertial frame of reference

Non-inertial frame of reference

Non-accelerated frame of reference

Accelerated frame of reference

5. An observer shoots parallel to a meter stick at very high (relativistic) speed and finds that the length of meter stick is

Greater than one meter

Less than one meter

One meter

A foolish question

6. According to special theory of relativity, speed of light in a vacuum

Is high for observers moving towards its source

Is high for observers moving away from its source

Same for all the observers in relative motion with respect to each other

Depends upon the uniform transnational motion of the source of light with respect to the observer

7. According to special theory of relativity, mass of an object moving relative to an observer with a velocity comparable to the velocity of light

Increases

Decreases

Remain constant

None of these

8. According to Einstein special theory of relativity the mass of a particle moving with speed of light will be

Zero

Double

Ten times

Infinite

9. Time interval between two events as recorder by an observer in relative motion with velocity comparable velocity of light with respect to the point of occurrence of the event.

Dilated

Shortens

Remains constant

None of these

10. With increase in the velocity of an object its mass will continuously

Increase

Decrease

Remain constant

None of these

11. According to special theory of relativity which one is not an absolute quantity?

Time

Mass

Height

Both A and B

12. Length contraction happens only

Along the direction of motion

Parallel to direction of motion

Both A and B

None of these

13. The phenomenon of black body radiations can be explained on the basis of

Wave theory

Classical theory

Bohr’s theory

Quantum theory

14. The S.I unit of plank’s constant is

Joule per sec

Joule per sec²

Joule — sec

Joule per sec³

15. A hot body will radiate maximum energy it its surface is

White and polished

Black and polished

White and rough

Black and rough

16. The S.I. unit of Stefan’s constant is

W/m² K⁴

J/m s K⁴

N/m² K⁴

J/m² K⁴

17. Which of the following statements is wrong?

Stefan’s constant is the same for all black bodies

Thermal radiation travel with the speed of 3 x 10⁵ m/s

Thermal radiation exhibit diffraction

Stefan’s law is applicable for all heated bodies

18. As the temperature of black body is raised the wavelength corresponding to maximum intensity

Shifts towards loner wavelength

Shifts towards shorter wavelength

Remain the same

Shifts towards longer as well as shorter wavelengths

19. Stopping potential for a metal surface in case of photoelectric emission depends on

The threshold frequency for the metal surface

The intensity of incident light

The frequency of incident light and work function of the metal surface

All of these

20. Tick the right statement

No photo electronic emission takes place if the frequency of radiation however intense it may be is less than a certain critical value called threshold frequency

Threshold frequency depends upon the nature of the metal surface

Maximum energy of a photoelectron is a function of frequency rather than intensity of radiation

All of these

21. A device based on photoelectric effect is called

Photo sensitive detection

Photo diode

Photosynthesis

Photo cell

22. In a photoelectric effect monochromatic light is incident on a metal surface. If incident light of twice the intensity but of same wavelength the kinetic energy of the emitted electron

Becomes double

Remains same

Becomes half

First increases then decreases because curvilinear graph

23. If the wavelength of incident radiation is increased in photoemission then

The maximum kinetic energy of the photoelectrons increases

The minimum kinetic energy of the photoelectrons decreases

The minimum kinetic energy of the photoelectrons Increases

The average kinetic energy of the photoelectrons decreases

24. When light of suitable frequency falls on the surface of a metal electrons are emitted from it, this phenomenon is known as

Compton effect

Thermionic emission

Photo multiplier effect

Photoelectric effect

25. Minimum frequency required to initiate photoelectric effect is called

Minimum frequency

Maximum frequency

Threshold frequency

Quantum frequency

Page 2 of 5

26. The value of work function depends upon

Frequency of incident light

Wave length of incident light

Nature of metal surface

Time for which metal is exposed

27. In photoelectric effect light exhibits

Wave nature

Particle nature

Neither wave nor particle nature

Particle as well as wave nature

28. In Compton effect frequency of scattered photon is

Less than the frequency of incident photon

Greater than the frequency of incident photon

Equal to the frequency of incident photon

None of these

29. The change in frequency of scattered photon depends upon the

Wave length of incident light

Angle at which photon collides with electron

Angle of scattering

Frequency of incident light

30. The scattering of X — ray photo by an electron is called

Photoelectric effect

Scattering effect

Compton effect

Pair production

31. Compton effect proves the

Photon theory of light

Dual nature of light

Wave nature of light

Uncertain nature of light

32. The uncertainty in momentum & position is due to its

Property of matter and radiation

Two dimensional motion

Emission of certain wavelength

Very high velocity

33. In Compton scattering the change in wave length is max if

Angle of scattering is 90?

Angle of scattering is 60?

Angle of scattering is 180?

Angle of scattering is zero?

34. According to uncertainty principle, the product of uncertainties tp and Ax in the measurements of momentum and position respectively of a particle at a certain instant is of the order of

Plank’s constant

Rydberg constant

Joule’s constant

Stephan’s constant

35. Compton effect is associated with

a—rays

β—rays

X—rays

Positive rays

36. The phenomenon of pair production is

Lionization of neutral atom,

The production of an electron and a positron from y —rays

Ejection of an electron from a metal surface when exposed to ultraviolet Light.

Ejection of and electron from a nucleus.

37. De Broglie waves are associated with

Moving charged particles only

Moving neutral particles only

All moving particles

All particles whether in motion or at rest

38. Every motion is

Relative

Absolute

Zero

None of these

39. Classical physics is still valid in

Very small particles

Fast moving particles

Ordinary process

None of these

40. A frame of reference is any coordinate system to which measurements are taken as:

Correctly

Specifically

Relative

None of these

41. An accelerated from of reference is called

Inertial frame

None-inertial frame

Both a and b

None of these

42. General theory of relativity is applicable in the

Inertial frame of reference

Non-inertial frame of reference

Both frames of reference

None of these

43. Time dilation is the result of special theory of relativity in which

Time increases

Time decreases

Remains the same

None of these

44. 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

45. Exact time can be measured in

Inertial frame

None-Inertial frame

Stationary frame

None of these

46. Aging process of the human body is slowed by motion at

Very slow speed

Very high speed

Very high speed along a circular path

None of these

47. Earth’s orbital speed is

20 kms¯¹

30 kms¯¹

40 kms¯¹

50 kms¯¹

48. At low temperature, a body emits wavelength in the region of

Infra-red

Ultraviolet

Far-infra red

None of these

49. The platinum wire is changes to cherry red at

800°C

900°C

950°C

957°C

50. A body termed as black body when it

Reflects all radiations

Absorbs all radiations

Absorbs and radiates all radiations

None of these

Page 3 of 5

51. The relation λmax X T=Constant represents

Stepfen’s law

Planck’s law

Wein’s law

None of these

52. 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

53. Max Planck received the Nobel Prize in Physics in

1915

1918

1923

None of these

54. The energy of photon of radio waves in only about

10¯⁶ eV

10¯⁴ eV

10¯¹⁰ eV

10¯¹² eV

55. Photoelectric effect is the phenomenon is which electrons are emitted from the metal when

It is heated

Light falls

Electrons strikes

None of these

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

Work

Work Function

Power

Wavelength

57. When scattered X-ray photons are observed at θ = 90°, the Compton shift ∆λ equal to

Compton shift

Compton wavelength

Full wavelength

None of these

58. A phenomenon is which a low energy photon interact with metal and usually absorbed with the emission of an electron is known as

Compton effect

Pair production

Photoelectric effect

None of these

59. A very high energy photon (ϒ-rays) interact with matter and changes into

Electron

Positron

Pair of electron and positron

None of these

60. A positron is a particle having

Mass equal to electrons

Charge equal to electrons

Equal but opposite charge

A and C

61. Light in short is the most refined form of

Water

Matter

Heat

None of these

62. The diffraction patterns can also been observed in Davisson and Germer experiment with

Hydrogen atoms

Helium atoms

Protons

All of these

63. A 50 kV microscope gives the resolution of

0.4 to 2nm

0.3 to 3 nm

0.5 to 1 nm

None of these

64. The angle of scattering for which the Compton shift is maximum

45°

90°

180°

270°

65. A photoelectric cell converts

Electrical energy to light energy

Light energy to light energy

Light energy to electrical energy

Light energy to elastic energy

66. The essential distinction between X-rays and ϒ-rays is that

ϒ-rays have smaller wavelength than X-rays

ϒ-rays emanate from nucleus while X-rays emanate from outer part of the atom

ϒ-rays have greater ionizing power than X-rays

ϒ-rays are more penetrating than X-rays

67. Light of wavelength 5000 Å falls on a sensitive plate with photoelectric work function of 1.9 eV. The kinetic energy of the photoelectron emitted will be

0.58 eV

2.48 eV

1.24 eV

1.16 eV

68. Sodium surface is subjected to ultraviolet and infrared radiations separately and the stopping potential of photoelectrons determined. Then the stopping potential

Is equal in both cases

More when ultraviolet is used

More when infrared is used

May be more or less for ultraviolet depending upon its intensity as compared to the intensity of infrared light

69. Which of the following is not dependent on the intensity of incident radiation in a photoelectric experiment?

Work function of the surface

Amount of photoelectric current

Stopping potential will be reduced

Maximum K.E. of photoelectron

70. As the intensity of incident light increases

Photoelectric current increases

Photoelectric current decreases

Kinetic energy of emitted photo electrons increases

Kinetic energy of emitted photo electrons decreases

71. The production of X-rays is due to

The collision of electrons with the target atom due to transfer of momentum

The collision of electrons with the target atom due to transfer of energy

The transition of electrons of heavy target atoms from high to low energy level on striking with electrons

None of these

72. The slope of frequency of incident light and stopping potential for a given surface will be

h/e

73. X-rays from X-ray tube

Will be monochromatic

Will have all possible wavelengths less than a certain longest wavelength

Will have all possible wavelengths greater than a certain shortest wavelength

Will have all wavelengths between the longest and the shortest wavelength

74. The wavelength of a photon, an electron and a uranium nucleus are equal. The minimum energy is associated with

Electron

Photon

Uranium

Equal in all cases

75. Cathode rays are identical to

ϒ-rays

X-rays

Radio waves

Cosmic rays

Page 4 of 5

76. Cathode rays striking the walls of a discharge tube cause

Phosphorescene

Fluorescence

Anodization

Breakage of discharge tube

77. The mass of the electron is m, its charge e and it is accelerated from rest through a potential difference V. The kinetic energy of the electron in joules will be

m e V

None of these

78. The speed of cathode rays is

Equal to speed of light

Greater than speed of light

Less than speed of light

May be less than, greater than or equal to speed of light

79. A television resembles closely with

A cathode ray tube

A rectifier

An oscillator

A radio telescope

80. Which of the following cannot be accelerated by a cyclotron?

Ion

Proton

Neutron

α-particle

81. What do we determine with mass spectrograph?

Charge

Mass

Specific charge

Wavelength

82. Which of the following radiation has the least wavelength?

β-rays

α-rays

X-rays

ϒ-rays

83. If the frequency of incident light in a photoelectric experiment is doubled

Maximum KE of photoelectrons is just doubled

Maximum KE of photoelectrons remains same

Maximum KE will be more than doubled

Maximum KE is halved

84. 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

85. 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

86. 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

87. 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

88. 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

89. 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

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

Charge of electron

Mass of electron

Revolution of electron around the nucleus

Speed of electrons

91. Rate of photoelectric emission is proportional to

Intensity of incident radiations

Frequency of incident radiations

Square of the frequency of incident radiations

Square of intensity of incident radiations

92. For photoelectric emission to take place

Frequency of incident radiations 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

93. 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

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

Photo-electric effect

Interference

Refraction

Polarization

95. When X-rays pass through 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. 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

97. 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

98. The stopping potential depends on

Intensity of incident light

Frequency of incident light

Both A and B

Neither A nor B

99. The phenomenon inverse to photoelectric effect is

Compton effect

Raman effect

Pair production

Production of X-rays

100. 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

Page 5 of 5

101. The mass of the particle moving with velocity of light is

Zero

Infinite

Finite

Unit

102. 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

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

Special theory of relativity

Quantum theory

Corpuscular theory

Bohr’s theory

104. The velocity of photon is

3 x 10⁸ ms¯¹

3 x 10⁸ cms¯¹

3 x 10⁸ ms¯²

3 x 10⁸ cms¯²

105. 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

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

Rest mass

Frequency of incident light

Momentum

Wavelength

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

Particles

Waves

Both Particles and Waves

None of these

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

Annihilation

Pair production

Compton Effect

Photoelectric Effect

109. “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 called

Pauli’s Exclusion Principle

Heisenberg Uncertainty

Photoelectric Effect

Compton Effect

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

Compton Effect

Photoelectric Effect

Pair production

Annihilation

111. Compton Effect is a phenomenon in which electromagnetic waves exhibit

Wave nature

Particle nature

Both Wave nature and Particle nature

None of these

112. 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

113. 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

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

Photoelectric Effect

Annihilation

X-rays Production

Compton Effect

115. 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

116. An electric eye operates because of

The Compton effect

ϒ-radiations

Photoelectric effect

Radiations pressure

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