FSC Physics MCQs Chapter 19 Class 12

Created on February 07, 2022

Physics Ch 19 Class 12 Dawn of Modern Physics

1 / 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

2 / 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

3 / 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

4 / 87

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

Increased

Decreased

Same

None

5 / 87

Mass of a body with speed of light approaches to:

Ze ro

Infinity

Remains same

None of these

6 / 87

Value of h Is:

1.05 x 10^34

6.63 x 10^34

2.78 x 10.^19

None of these

7 / 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

8 / 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

9 / 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

10 / 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

11 / 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

12 / 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

13 / 87

Which of the following Is correct?

Only I Is correct

Only II Is correct

Both are correct

None of these

14 / 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

15 / 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

16 / 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

17 / 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

18 / 87

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

Maxwell

Newton

Plank

Einstein

19 / 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

20 / 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

21 / 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

22 / 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

23 / 87

Compton shift is maximum at:

PMC 2021 Tested
Physics
Dawn of Modern Physics
Elimination Tool:

A) 180°

B) None

C) 0°

D) 90°

24 / 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

25 / 87

Which of the following waves has highest speed?

Micro waves

Gamma Rays

Infra-red

All have same speed

26 / 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

27 / 87

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

283

2.83

28.3

None

28 / 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

29 / 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

30 / 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

31 / 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

32 / 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

33 / 87

The absolute standard of rest is:

Earth

Sun

Galaxy

Non- existent

34 / 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

35 / 87

theory of was Relativity proposed by

Karl Heisenberg

Einstein

Davisson and Germer

Arthur Holly

36 / 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

37 / 87

Which of following has greatest energy

Microwave

) Radio waves

Ultraviolet

Infrared

38 / 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

39 / 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

40 / 87

The maximum Compton shift Is at

0 degrees

90 degrees

180 degrees

45 degrees

41 / 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

42 / 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

43 / 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

44 / 87

Which behaves as a particle as well as wave

Electron

Atom

Molecule

) All of these

45 / 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

46 / 87

A Black body is?

Bad absorber

Ideal absorber

Ideal radiator

Both b and c

47 / 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

48 / 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

49 / 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

50 / 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

51 / 87

Earth is a/an frame of reference

Inertial

Non-inertial

Both

None

52 / 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

53 / 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

54 / 87

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

Einstein

Bohr

Planck

Dirac

55 / 87

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

Einstein

Planck

Compton

Pringshiem

56 / 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

57 / 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

58 / 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

59 / 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)

60 / 87

Scattering of photon by electron is termed as:

Photoelectric effect

Pair production

Annihilation

Compton effect

61 / 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

62 / 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

63 / 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

64 / 87

Presence of Photon was confirmed by

Uncertainty principle

De Broglie

Photo electric effect

Compton effect

65 / 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

66 / 87

Who proposed matter waves?

De Broglie

Einstein

Stephen hawking

Lewis

67 / 87

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

60

30

90

120

68 / 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

69 / 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

70 / 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

71 / 87

Black body radiations were first observed by:

Maxwell

Planks

Lummer

None of these

72 / 87

Which of the following color has maximum energy?

Green

Blue

Red

Orange

73 / 87

Sunlight will emit photo electrons when striking which of the following

Plastic

Water

Wood

Metallic object

74 / 87

In E = aT4 E stands for??

Electric field

Energy per unit area

Energy

Energy per second per unit area

75 / 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

76 / 87

The stopping potential depends on

Intensity of incident light

Frequency of Incident light

Both a and b

None of these

77 / 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

78 / 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

79 / 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

80 / 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

81 / 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

82 / 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

83 / 87

) Twin paradox Is consequence of?

Time dilation

Mass dilation

Length dilation

None of these

84 / 87

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

Einstein

Planck

Compton

Pringshiem

85 / 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

86 / 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

87 / 87

Black body emits which of the following radiations:

Visible light

Infra-red

UV

All electromagnetic radiations

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