# 12th Class Physics Mcqs Chapter no 19 | Physics Mcqs For Class 12th Mcqs 2021 with answers pdf

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Chapter 19

DAWN OF MODERN

Encircle the most appropriate answer among the following option

I.          The classical physics is based on the laws of choose which one is correct:

(a) Quantum mechanics

(b) Newtonian mechanics

(c) Relativistic mechanics

(d) None of these

2.         Mathematical foundations for electromagnetic waves was provided by.

(a) Hertz

(b) Ampere

(c) Maxwell

(d) Newton

3.         Mathematical formulation for electromagnetic waves is given the name choose which one is correct:

(a) Hamiltons equation

(b) Langrange’s equation

(c) Maxwell’s equation

(d) None of these

4.         Which one of the following waves require a material medium for their propagation choose which one is correct:

(a) X-rays

(b) Light waves

(c) Y-prays

(d) Sound waves

5.         Which one of the following scientists regarded light as electromagnetic waves choose which one is correct:

(a) Maxwell

(b) de-Broglie

(c) Newton

(d) Galileo

6.         Which one of the following paved the way for modern physics choose which one is correct:

(a) Newtonian mechanics

(b) Theory of relativity

(c) Quantum theory

(d) All of above

7.         Absolute motion cannot be detected choose which one is correct:

(a) In different frame of reference

(b) Its own frame of reference

(c) Both in its frame and different frame

(d) None of these

8.         Point out the formulation that does not depend the choice of reference frames choose which one is correct:

(a) Velocity of object

(b) Newton’s law of motion

(c) Quantum theory

(d) None of above

9.         An inertial frame of reference is that choose which one is correct:

(a) Which is at rest on earth

(b) Which moves with uniform velocity

(c) Whose acceleration is zero

(d) All of above

10.       A non-inertial frame of reference is that choose which one is correct:

(a) Is always at rest

(b) Moves with some acceleration

(c) Moves with uniform velocity

(d) None of these

Il.         Light was considered as electromagnetic waves by the scientist choose which one is correct:

(a) Newton

(b) Maxwell

(c) Hertz

(d)Gallilo

12.       All motions are choose which one is correct:

(a) Uniform

(b) Relative

(c) Absolute

(d)        Variable

13.       Newton’s laws of motion are valid choose which one is correct:

(a) In non-inertial frame

(b) In inertial frame

(c) Both (a) and (b)

(d) None of these

14.       The concept of direction is purely choose which one is correct:

(a) Relative

(b) Absolute

(c) Relative to the motion

(d) None of these

15.       Due to relative motion of observer and the frame of reference of events time always choose which one is correct:

(a) Dilates itself

(b) Stretches itself

(c) Both (a) and (b)

(d) None of these

16.       The dilation of time applies to the timing process which are choose which one is correct:

(a) Chemical

(b) Biological

(c) Physical

(d) All of these

17.       Aging process of a human body choose which one is correct:

(a) Becomes fast

(b) Becomes slow

(c) No change

(d) None of these

18.       Mass of an object is choose which one is correct:

(a) Constant quantity

(b) Varying quantity

(c) Depends upon the speed of light

(d) None of these

19.       Earth orbital speed is choose which one is correct:

(a) 30 cm/s

(b) 30 km/s

(c) 30 m/s

(d) 0.3 m/s

20.       When the atomic particles are moving with velocities approaching that of light choose which one is correct:

(a) Newton’s laws become valid

(b) Newton’s laws become invalid

(c) Relativistic effects become prominent

(d) None of these

21.       From m =  that to get even a small increase in mass of an object, we require choose which one is correct:

(a) Very small changes in energy

(b) Large changes in energy

(c) Small changes in energy

(d) No change in energy

22.       In 1905, the special theory of relativity was proposed by choose which one is correct:

(a) Clark Maxwell

(b) de-Broglie

(c) Bohr

(d) Einstein

23.       Which one of the following physical quantities change with relativistic speed choose which one is correct:

(a) Length

(b) Time

(c) Mass

(d) All of above

24.       If an object moves with speed of light, its mass becomes choose which one is correct:

(a) Zero

(b) Infinity

(c) No change

(d) None of these

25.       The speed of light in free space is choose which one is correct:

(a) 3 x 108 m/s

(b) 3 x 107 m/s

(c) 3 x 109 m/s

(d) 3 x 106 m/s

26.       Due to the relative motion of observer and frame of reference, time choose which one is correct:

(a) Contracts

(b) Dilates

(c) Constant

(d) Uniform

27.       Earth is considered as choose which one is correct:

(a) Inertial fame of reference

(b) Non-inertial frame of reference

(c) Both (a) and (b)

(d) None of these

28.       Any coordinate system relative to which results are taken is known as choose which one is correct:

(a) Zero point

(b) Frame of reference

(c) Infinity point

(d) None of these

29.       The special theory of relativity is based upon choose which one is correct:

(a) 3 postulates

(b) 2 postulates

(c) 4 postulates

(d) None of these

30.       According to special theory of relativity all laws of physics are same in all choose which one is correct:

(a) Accelerated frames

(b) None accelerated frames

(c) Non inertial frames

(d) None of these

31.       The special theory of relativity is applicable to the objects moving with maximum velocity choose which one is correct:

(a) Less than speed of light

(b) Equal to speed of light

(c) More than speed of light

(d) None of these

32.       Radiations are always emitter or absorbed in the form of packet of energy. This is a statement of choose which one is correct:

(a) Stefan’s law

(b) Planck’s quantum law

(c) Einstein law

(d) None of these

33.       Which is a good absorber of heat radiation would be choose which one is correct:

(a) A black body

(b) A polished plate

(c) A white plate

(d) None of the above

34.       Black bodies are formed of choose which one is correct:

(a) Reflecting solid objects

(b) Metals

(c) No-reflecting objects

(d) Non-metals

35.       A black body becomes white at temperature choose which one is correct:

(a) 13000C

(b) 9000

(c) 15000C

(d) 16000C

36.       When an object moves with speed of light, its length choose which one is correct:

(a) Remain unchanged

(b) Increases

(c) Decreases

(d) None of these

37.       If an object moves with speed of light, then its apparent length becomes choose which one is correct:

(a) Zero

(b) Larger

(c) Smaller

(d) Infinity

38.       A body emits radiation which is of long or wavelength in visible infrared region at choose which one is correct:

(a) Low temperature

(b) High temperature

(c) At constant temperature

(d) None of these

39.       According to special theory of relativity, mass and energy are different quantities and choose which one is correct:

(a) Non-inter convertible

(b) Inter convertible

(c) No change

(d) None of these

40.       The nature of radiation emitted from a hot body depends upon choose which one is correct:

(a) Temperature

(b) Material

(c) Length

(d) Mass

41.       At low temperature, the hot body emits the radiation of choose which one is correct:

(a) Shorter wavelength

(b) High energy

(c) Low energy

(d) Both (a) and (b)

42.       At high temperature, the hot body emits the radiation of choose which one is correct:

(a) High energy and shorter wavelength

(b) Longer wavelength and high energy

(c) Low energy and shorter wavelength

(d) Shorter wavelength

43.       The radiations of longer wavelength choose which one is correct:

(a) Have low energy

(b) Have high energy

(c) At high temperature

(d) Both (a) and (b)

44.       When platinum wire is heated, then it become     at temperature 5000 C.

(a) White

(b) Green

(c) Yellow

(d) Dull red

45.       Black colour is choose which one is correct:

(a) Good absorber of heat

(c) Both (a) and (b)

(d) None of these

46.       For a black body, the product ofkm and T known as choose which one is correct:

(a) Wien’s constant

(b) Planck’s constant

(c) Davison constant

(d) Lumber’s constant

47.       The value of Wien%s constant is measured in choose which one is correct:

(a) m.K

(b) mk-1

(c)  m-1K

(d) m-1K-1

48.       In SI units, the value of Wien’s constant is choose which one is correct:

(a) 9.8 mK

(b) 2.9 x 10-3 mK

(c) 6.63 x 1034 mK

(d) 3 x 10-8

49.       The ratio of the energy E to the corresponding frequency f of the radiation emitted or absorbed is known as choose which one is correct:

(a) Boltzman constant

(b) Steffen’s constant

(c) Wien’s constant

(d) Planck’s constant

50.       Max Planck awarded the noble prize for his discovery of energy quanta in.

(a) 1918 A.D

(b) 1920 A.D

(c) 1718 A.D

(d) 1818 A.D

51.       In Sl units the value of Stefen’s constant is choose which one is correct:

(a) 6.63×10-34 Wm-2k-4

(b) 2.9 x 10-3  Wm-2k-4

(c) 5.67x 10-8  Wm-2k-4

(d) 3×10-8  Wm-2k-4

52.       The wavelength corresponding to maximum intensity of radiation shifts steadily towards shorter wavelength choose among following choose which one is correct:

(a) The temperature decreases

(b) The temperature increases

(c) The temperature is constant

(d) The temperature is zero

53.       The idea of matter waves was given by choose which one is correct:

(a) Einstein

(b) de-Broglie

(c) Planck

(d)        Davison and Germer

54.       The nature of radiation emitted by a body depends upon choose which one is correct:

(a) Mass

(b) Temperature

(c) Volume

(d) Pressure

55.       At high temperature, a body emits radiations of choose which one is correct:

(a) Long wavelength

(b) Small wavelength

(c) Intermediate wavelength

(d) None of these

56.       The electrons behave as waves because they can be choose which one is correct:

(a) Deflected by electric field

(b) Ionize as gas

(c) Deflected by magnetic field

(d) Diffracted by crystals

57.       At low temperature, a body generally emit radiations of choose which one is correct:

(a) Long wavelength

(b) Small wavelength

(c) Intermediate wavelength

(d) None of these

58.       If the momentum of particle is doubled, than its de-Broglie wavelength choose which one is correct:

(a) Doubles

(b) Halves

(c) Remain unchanged

(d) None of these

59.       In Davison and Germer experiment, nickel crystal acts as a choose which one is correct:

(a) Perfect reflector

(b) Perfect absorber

(c) Two dimensional grating

(d) Three dimensional grating

60.       The Davison and Germer experiment relates to choose which one is correct:

(a) Diffusion

(b) Interference

(c) Polarization

(d) Electron diffraction

61.       In Davison and Germer experiment, the angle between incident beam and diffracted beam called choose which one is correct:

(a) Angle of incidence

(b) Glancing angle

(c) Angle of diffraction

(d) Angle

62.       In Davison and Germer expert, the angle which the incident beam makes with the normal to the nicked crystal is choose which one is correct:

(a) 690

(b) 650

(c) 900

(d)1800

63.       The uncertainty principle was given by choose which one is correct:

(a) de-Broglie

(b) Heisenberg

(c) Einstein

(d) Max Planck

64.       The uncertainty principle applicable to choose which one is correct:

(a) Small system only

(b) Large system only

(c) Sub-atomic particles only

(d) Both sub-atomic and large system

65.       The uncertainty principle is applicable only when choose which one is correct:

(a) Momentum is measured only

(b) Position is measured only

(c) Both position and momentum are measured

(d) None of these

66.       The uncertainty principle is significant for choose which one is correct:

(a) Macroscopic bodies

(b) Microscopic bodies

(c) Both microscopic and microscopic

(d) None of these

67.       The uncertainty principle relates uncertainties in the measurements of energy and choose which one is correct:

(a) Velocity

(b) Time

(c) Momentum

(d) Mass of the particle

68.       The uncertainty in the location of a particle is equal to its de-Broglie wavelength, then uncertainty in its velocity will be equal to choose which one is correct:

(a) Four times its velocity

(b) Twice its velocity

(c) Half of its velocity

(d) Its velocity

69.       Photoelectric effect was discovered by choose which one is correct:

(a) Einstein

(b) G.P Thomson

(d) Bohr

70.       The photoelectric effect predicts that light is made of choose which one is correct:

(a) Photons

(b) Neutrons

(c) Protons

(d) None of these

71.       The phenomenon of photoelectric effect was first explained by choose which one is correct:

(a) Einstein

(b) Bohr

(c) Maxwell

(d) Planck

72.       The way through which electromagnetic radiation or photons interact wit 7/16 their choose which one is correct:

(a) Frequency

(b) Energy

(c) Wave length

(d) All of the above

73.       The process through which photons can interact with matter is choose which one is correct:

(a) Photo electric effect

(b) Compton effect

(c) Pair production

(d) Any of these

74.       The amount of photoelectric current depends upon choose which one is correct:

(a) Intensity of light beam

(b) Energy of incident photons

(c) Stopping potential

(d) All of the above

75.       While demonstrating the photoelectric effect the stopping potential is achieved when choose which one is correct:

(a) Anode is made more and more positive

(b) Battery is switched off

(c) Photo electric current becomes zero

(d) None of these

76.       If the photoelectric current is goes on decreasing it means that choose which one is correct:

(a) Photons are attracted by the anode

(b) Photoelectrons are attracted by the anode

(c) Photoelectrons are repelled by the anode

(d) Electrons are repelled by the anode

77.       Threshold frequency is the choose which one is correct:

(a) Varies from metal to metal

(b) Minimum frequency below which no electron is emitted

(c) Same for all metals

(d) Both (a) and (b)

78.       Einstein was received the noble prize in the basis of choose which one is correct:

(a) Quantum theory of light

(b) Theory of relativity

(c) Explanation of photoelectric effect

(d) Energy band theory

79.       The unit of work function is choose which one is correct:

(a) Electron volt

(b) Ampere

(c) Volt cell

(d) Hz

80.       A photocell can be used to operate choose which one is correct:

(a) Counting system

(b) Security system

(c) Automatic door system

(d) All of above

81.       A photon is a choose which one is correct:

(a) Positively charged particle

(c) Unit of Energy

(d) Unit of wavelength

82.       When the stopping potential is applied to the anode of photocell, no current is ab mean choose which one is correct:

(a) The emission of photoelectrons stops

(b) The photoelectrons are emitted but are reabsorbed by the photo cathode itself

(c) Both (a) and (b)

(d) None of these

83.       The best metal to be used for photoemission is choose which one is correct:

(a) Cesium

(b) Lithium

(c) Potassium

(d) Sodium

84.       Photoelectric effect was discovered by choose which one is correct:

(a) Lenard

(b) Einstein

(c) Hertz

(d) Neutron

85.       Which conservation law is obeyed in Einstein photoelectric equation choose which one is correct:

(a) Momentum

(b) Charge

(c) Mass

(d) Energy

86.       If the energy of photon is 10 eV and work function is 5 eV, then the a value of stoppi will be choose which one is correct:

(a) 50 V

(b) 2 V

(c) 5 V

(d) 15 V

87.       When a photon of energy 7 ev is made incident on a metal then emitted electron is stopped by a stopping potential -5.5 V. The work function of the metal will be choose which one is correct:

(a) 12.5 ev

(b) -1.5 ev

(c) 37.5 ev

(d) 1.5

88.       The relation between work function and maximum energy of photoelectrons was discovered by choose which one is correct:

(a) Stefan

(b) Marely

(c) Planck

(d) Einstein

89.       Which of the following makes use of photoelectric effect choose which one is correct:

(a) Television camera

(d) CRO

90.       The work function for photoelectric effect choose which one is correct:

(a) Same for all metals

(b) Depends on the frequency

(c) different for different metals

(d) None of these

91.       In photoelectric emission, the energy of emitted electron is choose which one is correct:

(a) Larger than that of photon

(b) Less than that of photon

(c) Same as that of photon

(d) None of these

92. In Compton effect, the wavelength of scattered photons as compared to the wavelength of incident x-rays is choose which one is correct:

(a) Larger

(b) Smaller

(c) Constant

(d) None of these

93.       Compton considered that x-rays consist of choose which one is correct:

(a) Neutrons

(b) Protons

(c) Electrons

(d) Photons

94.       The photoelectric current depends upon choose which one is correct:

(a) Intensity of the incident radiation

(b) Frequency of incident photon only

(c) Intensity and frequency of incident radiation

(d) None of these

95.       The velocity of the photoelectron depends upon choose which one is correct:

(a) Intensity of incident photon

(b) Frequency of incident photon

(c) Intensity as well as frequency of incident photon

(d) None of these

96.       The study of photoelectric effect is useful for understanding choose which one is correct:

(a) The quantum nature of matter

(b) The wave nature of matter

(c) Bohr’s atomic model

(d) Structure of the nucleus

97.       The stopping voltage in photoelectric effect depends upon choose which one is correct:

(a) Nature of the metal surface

(b) Intensity of incident light

(c) Frequency of incident light

(d) Frequency as well as metal surface

98.       The cut off voltage is independent of intensity of incident light if choose which one is correct:

(a) Material of electrode is fixed

(b) Frequency of incident light

(c) Frequency and material of electrode are fixed

(d) None of these

99.       The photoelectric threshold frequency depends upon.

(a) Frequency

(b) Nature of material

(c) Intensity of light

(d) None of them

100.     The maximum number of the photoelectrons released in photocell is independent of choose which one is correct:

(a) Frequency of incident light

(b) Nature of the cathode surface