Physics Dawn of Modern Physics MCQs Chapter 8 Class 12

Physics Dawn of Modern Physics MCQs Chapter 8 Class 12

Dawn of Modern Physics is an important chapter of Class 12 Physics and is essential for free preparations for entry tests and FSC Part-II exams. It is frequently included in MDCAT, NUMS, AKU, NUST, UET ECAT, and FSC board examinations. This chapter covers key topics such as dual nature of matter and radiation, photoelectric effect, atomic models, and quantum theory. Many students rely on entry test MCQs and practice tests to strengthen their conceptual understanding.

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Created on February 07, 2022 By Ali Durrani

Physics Ch 19 Class 12 Dawn of Modern Physics

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1 / 87

The phenomena in which certain metals emit electrons when exposed to high-frequency light is known as?

NTS 2014
Physics
Dawn of Modern Physics
Elimination Tool:

A) Photoelectric Effect

B) Compton’s Effect

C) Henry's Effect

D) Principle of Relativity

2 / 87

Scattering of photon by electron is termed as:

Photoelectric effect

Pair production

Annihilation

Compton effect

3 / 87

Compton shift is maximum at:

PMC 2021 Tested
Physics
Dawn of Modern Physics
Elimination Tool:

A) 180°

B) None

C) 0°

D) 90°

4 / 87

Minimum energy required to eject an electron from metal surface is called:

UHS 2019
Physics
Dawn of Modern Physics
Elimination Tool:

A) Stopping potential

B) Electromotive force

C) Work function

D) Threshold frequency

5 / 87

The absolute standard of rest is:

Earth

Sun

Galaxy

Non- existent

6 / 87

Earth is a/an frame of reference

Inertial

Non-inertial

Both

None

7 / 87

An electron moving with velocity v has momentum 3 x 10 -26 Kg.m/s. The de Broglie wavelength associated with it is ______. Value of h = 6.63 x 10-34 is.

NTS 2019
Physics
Dawn of Modern Physics
Elimination Tool:

A) 24.1 nm

B) 22.14 m

C) 22.1 nm

D) 22.1 mm

8 / 87

The stopping potential depends on

Intensity of incident light

Frequency of Incident light

Both a and b

None of these

9 / 87

A 5 watt LED bulb converts 80% of the power into light photons wavelength 660 nm. What is the number of photons emitted from the bulb in one second.

UHS 2018
Physics
Dawn of Modern Physics
Elimination Tool:

A) 5.8 x 1034

B) 7.5 x 1018

C) 6.6 x 107

D) 1.3 x 1019

10 / 87

The energy of an X-ray quantum of wavelength 1.0 x 10-10 m is:

NTS 2012
Physics
Dawn of Modern Physics
Elimination Tool:

A) 1.99 x 10-15 J

B) 3 x 108 J

C) 6.6 x 10-34 J

D) 19.89 x 10-26 J

11 / 87

Planck’s constant is analogous to:

PMC Practice 6
Physics
Dawn of Modern Physics
Elimination Tool:

A) Inertia

B) Wave nature

C) Angular momentum

D) Linear momentum

12 / 87

In order to produce pair production the minimum energy of photon required is:

NTS 2019
Physics
Dawn of Modern Physics
Elimination Tool:

A) 1.02 KeV

B) 1.02 MeV

C) 10.2 KeV

D) 1.00 MeV

13 / 87

In Compton’s effect the wavelength of the scattered photon is

Increased

Decreased

Same

None

14 / 87

X-rays are used to investigate:

PMC Sample 3
Physics
Dawn of Modern Physics
Elimination Tool:

A) Crystals

B) Molecules

C) Ions

D) Electrons

15 / 87

Gamma rays cause photoelectric emission when their energy is

Greater then 5 Mev

Less than 0.5 Mev (

None of these

Equal to 0.5 Mev

16 / 87

Which behaves as a particle as well as wave

Electron

Atom

Molecule

) All of these

17 / 87

What would be Compton Wave shift if X-rays are scattered at an angle of 90 degree?

Equal to Compton wavelength

Zero

Maximum

Minimum

18 / 87

Which of following has greatest energy

Microwave

) Radio waves

Ultraviolet

Infrared

19 / 87

The spin of a photon is:

PMC 2021 Tested
Physics
Dawn of Modern Physics
Elimination Tool:

A) 1/4

B) 0

C) 1/2

D) 1

20 / 87

Momentum of a photon is?

PMC Practice 2
Physics
Dawn of Modern Physics
Elimination Tool:

A) 0

B) λ

C) hf/c

D) mv

21 / 87

Sunlight will emit photo electrons when striking which of the following

Plastic

Water

Wood

Metallic object

22 / 87

Value of Wien’s constant is?

2.9 x 10^3 K

2.9 x 10^3 K/m

2.9 x 10^3 m K

2,9 x 10^3 m

23 / 87

Which statement is universally correct?

Motion can alter time but not space

Motion cannot alter both time and space

Motion can alter time and space

None of these

24 / 87

If temperature on Kelvin scale Is reduced to half, what would be the effect on the energy of radiations?

Increase 8 times

Decrease 8 times

Increase 16 times

Decrease 16 times

25 / 87

What will be the energy of electron travelling at 10^7 m/s

283

2.83

28.3

None

26 / 87

Which group consists of only electromagnetic waves?

PMC Sample 1
Physics
Dawn of Modern Physics
Elimination Tool:

A) Microwaves, radio waves, and infra red

B) Microwaves, radio waves, and sound

C) Microwaves, water waves, and infra red

D) Waves on a rope, radio waves, and infra red

27 / 87

The uncertainty in momentum and position is due to its:

PMC Sample 1
Physics
Dawn of Modern Physics
Elimination Tool:

A) Property of matter and radiation

B) Two dimensional motion

C) Extreme velocities

D) Small size

28 / 87

Which of the following waves has highest speed?

Micro waves

Gamma Rays

Infra-red

All have same speed

29 / 87

The energy equivalent to 0.9 mg is? a) 9 x 1091 b) 8.1 x 10″J •

9 x 10^9

8.1 x 10^13

8.1 x 10^59

None

30 / 87

Presence of Photon was confirmed by

Uncertainty principle

De Broglie

Photo electric effect

Compton effect

31 / 87

Black body radiations were first observed by:

Maxwell

Planks

Lummer

None of these

32 / 87

In Einstein’s theory, the deflection of light is predicted to be exactly as great as it is according to Newton’s theory

Four times

Thrice

One and a half time

Twice

33 / 87

A photosensitive material would emit electrons if it is excited by a photon beyond a threshold. To cross the threshold, what should be increased?

PMC 2021 Tested
Physics
Dawn of Modern Physics
Elimination Tool:

A) Wavelength of light

B) Frequency

C) Voltage of source

D) Intensity of light

34 / 87

Fluorescence is produced when cathode rays strike on:

PMC 2021 Tested
Physics
Dawn of Modern Physics
Elimination Tool:

A) Fe

B) MgO

C) I

D) ZnS

35 / 87

The Bohr’s postulate for stationary orbits of Hydrogen atoms _____. Here m is the mass of the electron, v velocity, r orbital, and h is Planck’s constant.

NTS 2019
Physics
Dawn of Modern Physics
Elimination Tool:

A) mr=nhv/2ℼ

B) mvr=nh/2ℼ

C) mvr=nh/2ℼr

D) mv=nhr/2ℼ

36 / 87

In Heisenberg Principle:

Position and Momentum cannot be measured accurately of sub-atomic particles

Position and Momentum cannot be measured accurately of electrons

position and Momentum can be measured accurately of electrons

Position and Momentum can be measured accurately of sub-atomic particles

37 / 87

Mass of a body with speed of light approaches to:

Ze ro

Infinity

Remains same

None of these

38 / 87

Heisenberg uncertainty principle states:

Position & Momentum of a particle can be accurately measured simultaneously

Position & Momentum of a particle can be accurately measured simultaneously only under certain condition

Position & Velocity of a particle can be accurately measured simultaneously

Position & Momentum of a particle cannot be accurately measured simultaneously

39 / 87

Who was awarded Nobel Prize (1921) for explanation of Photoelectric Effect?

Einstein

Planck

Compton

Pringshiem

40 / 87

The number of LED segments used in a calculator display:

NUMS 2015
Physics
Dawn of Modern Physics
Elimination Tool:

A) 8

B) 10

C) 7

D) None

41 / 87

In the Compton Scattering experiment the X-ray wavelength change Δλ is ___________. Here h is Planck constant, m rest mass of electron and θ is angle after scattering.

NTS 2019
Physics
Dawn of Modern Physics
Elimination Tool:

A) Δλ=h/moC(1+ Cosθ)

B) λ=h/moC(1 – Cos2θ)

C) Δλ=h/moC(1 – Cosθ)

D) Δλ=h/moC2(1 + Cosθ)

42 / 87

If frequency of incident light is increased beyond threshold frequency, keeping light intensity constant, then:

NUMS 2019 Reconduct
Physics
Dawn of Modern Physics
Elimination Tool:

A) Stopping potential increases

B) Stopping potential decreases

C) Stopping potential remains constant

D) Stopping potential becomes infinite

43 / 87

theory of was Relativity proposed by

Karl Heisenberg

Einstein

Davisson and Germer

Arthur Holly

44 / 87

Calculate the energy of a photon of wavelength 6600 Angstroms:

PMC Practice 5
Physics
Dawn of Modern Physics
Elimination Tool:

A) 0.3 x 10-19J

B) 3 x 10-19J

C) 30 x 10-19J

D) 300 x 10-19J

45 / 87

The existence of positron was discovered in the:

PMC Sample 3
Physics
Dawn of Modern Physics
Elimination Tool:

A) Thermal radiation

B) Cosmic radiation

C) Electromagnetic radiation

D) Non-electromagnetic radiation

46 / 87

Debroglie wavelength for an electron and proton moving at same speed are L and 1; respectively. And frequencies are Fe and Fp respectively. Which of the following is corrract.

Fe Lp

Le < Lp , Fp < Fe

Le < Lp, Fe = Fp

Le > Lp Fe>Fs

47 / 87

Candela is the luminous intensity, in the perpendicular direction of a surface _________ square meter of a black body at the temperature of freezing platinum under a pressure of 101325 newtons per square meter.

NTS 2013
Physics
Dawn of Modern Physics
Elimination Tool:

A) 1/300000

B) 1/600000

C) 1/900000

D) 1/1200000

48 / 87

According to Einstein, bodies and light rays follow a:

NUMS 2015
Physics
Dawn of Modern Physics
Elimination Tool:

A) Rectilinear path

B) Circular path

C) Geodesics

D) Parabolic

49 / 87

What will be the energy of an X-ray quantum of wave length 1.0 x 10-10 m?

NTS 2016 SMBBMC
Physics
Dawn of Modern Physics
Elimination Tool:

A) 0.6 x 10^-15 J

B) 1.98 x 10^-15 J

C) 3.7 x 10^-15 J

D) 4.7 x 10^-15 J

50 / 87

When an observer moves with velocity of light, relative to a timing device at rest, he would notice:

NUMS 2015
Physics
Dawn of Modern Physics
Elimination Tool:

A) Absolute time

B) Improper time

C) Infinite time

D) Proper time

51 / 87

Electromagnetic wave theory was proposed by:

NTS 2015 SMBBMC
Physics
Dawn of Modern Physics
Elimination Tool:

B) Fraunhoffer

C) Fresnel

D) Coulomb

E) Maxwell

52 / 87

Photocell is similar to:

PMC Sample 2
Physics
Dawn of Modern Physics
Elimination Tool:

A) Photoelectric effect

B) Compton effect

C) Photoluminescence

D) None of these options are correct

53 / 87

Black body emits which of the following radiations:

Visible light

Infra-red

All electromagnetic radiations

54 / 87

Light photons, each of energy 3.5 x 10-19J falls on the cathode of a photocell. The current through the cell is reduced to zero by taking the cathode to a potential +0.25 V relative to anode. The work function of the cathode is:

UHS 2018
Physics
Dawn of Modern Physics
Elimination Tool:

A) 3.35 x 10-19J

B) 3.5 x 10-19J

C) 3.25 x 10-19J

D) 3.1 x 10-19J

55 / 87

White light gives spectrum after undergoing:

PMC Sample 2
Physics
Dawn of Modern Physics
Elimination Tool:

A) Diffraction

B) Interference

C) Reflection

D) All of these options are correct

56 / 87

Gamma-ray (?) can produce ionization in which of the following way/s?

I. It may lose all its energy in a single encounter with the electron of an atom (Photoelectric effect).

II. It may lose only a part of its energy in an encounter (Compton effect).

III. Very few of very high energy ? ray photons may impinge directly on heavy nuclei, be stopped and annihilated giving rise to electron-positron pairs (The materialization of energy).

NTS 2013
Physics
Dawn of Modern Physics
Elimination Tool:

B) II only

C) III only

D) I and III only

E) I, II and III

57 / 87

Physics is an experimental science which depends heavily on:

NTS 2016 SMBBMC
Physics
Dawn of Modern Physics
Elimination Tool:

A) The objective observations

B) Measurement of natural phenomena

C) Study of chemical solutions only

D) Both A and B

58 / 87

The charge of a photon is:

PMC Sample 1
Physics
Dawn of Modern Physics
Elimination Tool:

A) 0

B) Positive

C) Negative

D) Positive/negative

59 / 87

Photoelectric effect is not produced by:

PMC 2021 Tested
Physics
Dawn of Modern Physics
Elimination Tool:

A) Beta rays

B) Gamma rays

C) X-rays

D) All of these

60 / 87

Calculate the energy of a photon, with a frequency of 3.0 x 1018 Hz.
(h = 6.63 x 10-34)

UHS 2019
Physics
Dawn of Modern Physics
Elimination Tool:

A) 19.89 x 10-16 J

B) 11.89 x 10-16 J

C) 1.89 x 10-16 J

D) 19.89 x 10-18 J

61 / 87

Who was awarded Nobel Prize (1921) for explanation of Photoelectric Effect?

Einstein

Planck

Compton

Pringshiem

62 / 87

Which light photon has the least momentum?

PMC Practice 6
Physics
Dawn of Modern Physics
Elimination Tool:

A) Red

B) Green

C) Yellow

D) Blue

63 / 87

In photo-emission from a metal, if light of λ is replaced by light of wavelength λ / 4 , the maximum kinetic energy of the photoelectrons.

UHS 2018
Physics
Dawn of Modern Physics
Elimination Tool:

A) Decreases by an amount equal to half of an incident photon of wavelength λ

B) Increases by an amount equal to four times energy of an incident photon of wavelength λ

C) Increases by an amount equal to the work function of the metal

D) Decreases by an amount equal to the energy of an incident photon of wavelength λ

64 / 87

Einstein was given a Nobel prize for:

PMC 2021 Tested
Physics
Dawn of Modern Physics
Elimination Tool:

A) Compton effect

B) Quantum theory

C) Photoelectric effect

D) Pair production

65 / 87

The electron shows purely a ____ when free.

PMC Sample 2
Physics
Dawn of Modern Physics
Elimination Tool:

A) particle nature

B) wave nature

C) dual nature

D) it transform to photon

66 / 87

What will be the energy in Joules, when an electron acquires a speed of 10 m/s?

NTS 2016 DUHS & JSMU
Physics
Dawn of Modern Physics
Elimination Tool:

A) 3.61 x 10-19J

B) 4.55 x 10-29 J

C) 5.13 x 10-19J

D) 6.13 x 10-19J

67 / 87

In E = aT4 E stands for??

Electric field

Energy per unit area

Energy

Energy per second per unit area

68 / 87

Plank׳s constant is analogus to:

PMC Sample 3
Physics
Dawn of Modern Physics
Elimination Tool:

A) Inertia

B) Wave nature

C) Angular momentum

D) Linear momentum

69 / 87

What will the de Broglie wavelength of a 150 g mass moving with a velocity of 50 m/s be?

PMC 2021 Tested
Physics
Dawn of Modern Physics
Elimination Tool:

A) 1000 m

B) 9 x 10⁻²⁵ m

C) 9 x 10⁻³⁵ m

D) 5 x 10⁻³⁵ m

70 / 87

Who proposed matter waves?

De Broglie

Einstein

Stephen hawking

Lewis

71 / 87

When photons are incident on a metal, electrons are emitted. The process is called:

NTS 2016 SMBBMC
Physics
Dawn of Modern Physics
Elimination Tool:

A) Photoelectric effect

B) Pair production

C) X-ray production

D) Gamma ray production

72 / 87

Which of the following Is correct?

Only I Is correct

Only II Is correct

Both are correct

None of these

73 / 87

Anti matter theory was proposed by: a) Einstein b) Bohr

Einstein

Bohr

Planck

Dirac

74 / 87

When an electron and its antiparticle positron come close enough to each other, they completely convert into radiation energy in the form of photons, this process is called:

NTS 2018
Physics
Dawn of Modern Physics
Elimination Tool:

A) Photoelectric current

B) Pair production

C) Annihilation of matter

D) Compton effect

75 / 87

The concept of work function was given by:

PMC Sample 2
Physics
Dawn of Modern Physics
Elimination Tool:

A) Bohr

B) Einstein

C) Rutherford

D) None of these option is correct

76 / 87

The photocell is similar to:

PMC Practice 5
Physics
Dawn of Modern Physics
Elimination Tool:

A) Photoelectric effect

B) Compton effect

C) Photoluminescence

D) None of these options is correct

77 / 87

Value of h Is:

1.05 x 10^34

6.63 x 10^34

2.78 x 10.^19

None of these

78 / 87

Minimum frequency below which no electrons are emitted from the metal surface is called ______ frequency.

NTS 2016 DUHS & JSMU
Physics
Dawn of Modern Physics
Elimination Tool:

A) Minimum

B) Angular

C) Maximum

D) Threshold

79 / 87

) Twin paradox Is consequence of?

Time dilation

Mass dilation

Length dilation

None of these

80 / 87

Name the scientist who won the noble prize for discovery of energy quanta

Maxwell

Newton

Plank

Einstein

81 / 87

The value and units of the Planck constant ‘h’ can be expressed as:

UHS 2019
Physics
Dawn of Modern Physics
Elimination Tool:

A) 3.63 x 10-34 Js

B) 6.63 x 10-34 Js-1

C) 6.63 x 10-34 Js

D) 6.63 x 10-43 Js

82 / 87

The maximum Compton shift Is at

0 degrees

90 degrees

180 degrees

45 degrees

83 / 87

Which of the following color has maximum energy?

Green

Blue

Red

Orange

84 / 87

A Black body is?

Bad absorber

Ideal absorber

Ideal radiator

Both b and c

85 / 87

If Compton shift is half of Compton wavelength, then the scattering angle would be:

120

86 / 87

The de Broglie wavelength of an electron travelling with a speed of 1.0 x 107m/s is equal to, (h=6.6 x 10-34 Js and me= 9.1 x 10-31 kg)

UHS 2018
Physics
Dawn of Modern Physics
Elimination Tool:

A) 7.3 x 1011m

B) 7.3 x 108m

C) 7.3 x 10-11m

D) 7.3 x 10-13m

87 / 87

The series limit for the Balmer series of hydrogen spectrum occurs at 3664 A. Calculate Ionization energy of hydrogen atom.

NTS 2013
Chemistry
Dawn of Modern Physics
Elimination Tool:

A) 21.7 x 10-19J

B) 6.626 x 10-34J

C) 5.425 x 10-19J

D) 3664 x 10-10J

Your score is

The average score is 56%

Importance of Modern Physics MCQs

Understanding Modern Physics helps students analyze experiments, solve numerical problems, and apply quantum principles. Moreover, MCQs often focus on photoelectric calculations, atomic models, and experimental observations. Practicing chapter-wise MCQs and short tests improves accuracy, speed, and confidence. Therefore, consistent practice ensures better performance in competitive exams.

Effective Strategy for Free Preparations

Students should revise formulas, understand experimental setups, and solve topic-wise MCQs regularly. In addition, attempting free tests and past questions helps identify important patterns and frequently asked questions. PLS Academy provides structured resources to support free entry test preparations for Physics Dawn of Modern Physics and other Class 12 Physics chapters.

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