# MCQs for Physics Class 12 with Answers Chapter 11 Dual Nature of Radiation and Matter

Students of class 12 Physics should refer to MCQ Questions Class 12 Physics Dual Nature of Radiation and Matter with answers provided here which is an important chapter in Class 12 Physics NCERT textbook. These MCQ for Class 12 Physics with Answers have been prepared based on the latest CBSE and NCERT syllabus and examination guidelines for Class 12 Physics. The following MCQs can help you to practice and get better marks in the upcoming class 12 Physics examination

## Chapter 11 Dual Nature of Radiation and Matter MCQ with Answers Class 12 Physics

MCQ Questions Class 12 Physics Dual Nature of Radiation and Matter provided below have been prepared by expert teachers of grade 12. These objective questions with solutions are expected to come in the upcoming Standard 12 examinations. Learn the below provided MCQ questions to get better marks in examinations.

Question. Monochromatic light of wavelength 667 nm is produced by a helium neon laser. The power emitted is 9 mW. The number of photons arriving per second on the average at a target irradiated by this beam is:
(a) 3 × 1016
(b) 9 × 1015
(c) 3 × 1019
(d) 9 × 1017

A

Question. A particle is dropped from a height H. The de Broglie wavelength of the particle as a function of height is proportional to
(a) H
(b) H1/2
(c) H0
(d) H –1/2

D

Question. In a photoelectric experiment the stopping potential for the incident light of wavelength 4000Å is 2 volt. If the wavelength be changed to 3000 Å, the stopping potential will be
(a) 2 V
(b) zero
(c) less than 2 V
(d) more than 2 V

D

Question. A proton and a-particle are accelerated through the same potential difference. The ratio of their de-Broglie wavelength will be
(a) 1 : 1
(b) 1 : 2
(c) 2 : 1
(d) 2 2 : 1

C

Question. A photoelectric cell is illuminated by a point source of light 1 m away. The plate emits electrons having stopping potential V. Then:
(a) V decreases as distance increase
(b) V increases as distance increase
(c) V is independent of distance (r)
(d) V becomes zero when distance increases or decreases

C

Question. The threshold wavelength for photoelectric emission from a material is 5200 Å. Photoelectrons will be emitted when this material is illuminated with monochromatic radiation from a:
(a) 50 watt infrared lamp
(b) 1000 watt infrared lamp
(c) 1 watt ultraviolet lamp
(d) 1 watt infrared lamp

C

Question. In the Davisson and Germer experiment, the velocity of electrons emitted from the electron gun can be increased by
(a) increasing the potential difference between the anode and filament
(b) increasing the filament current
(c) decreasing the filament current
(d) decreasing the potential difference between the anode and filament

A

Question. If E1, E2, E3 are the respective kinetic energies of an electron, an alpha-particle and a proton, each having the same de-Broglie wavelength, then
(a) E1 > E3 > E2
(b) E2 > E3 > E1
(c) E1 > E2 > E3
(d) E1 = E2 = E3

A

Question. In a photoelectric effect experiment, for radiation with frequency u0 with hu0 = 8eV, electrons are emitted with energy 2 eV. What is the energy of the electrons emitted for incoming radiation of frequency 1.25 u0 ?
(a) 1 eV
(b) 3.25 eV
(c) 4 eV
(d) 9.25 eV.

C

Question. When the speed of electrons increase, then the value of its specific charge
(a) increases
(b) decreases
(c) ramains unchanged
(d) increases upto some velocity and then begins to decrease

B

Question. The number of photoelectrons emitted for light of frequency ν (higher than the threshold frequency ν0) is proportional to:
(a) threshold frequency
(b) intensity of light
(c) frequency of light
(d) ν – ν0

B

Question. The work-function for a metal is 3 eV. To emit a photoelectron of energy 2 eV from the surface of this metal, the wavelength of the incident light should be:
(a) 6187 Å
(b) 4125 Å
(c) 12375 Å
(d) 2486 Å

D

Question. Relativistic corrections become necessary when the expression for the kinetic energy 1/2mv2 , becomes comparable with mc2, where m is the mass of the particle. At what de Broglie wavelength will relativistic corrections become important for an electron?
(a) λ = 10 nm
(b) λ = 10–1 nm
(c) λ = 10–4 nm
(d) λ = 10–6 nm

C, D

Question. Two particles A1 and A2 of masses m1, m2 (m1 > m2) have the same de Broglie wavelength. Then
(a) their momenta are the same
(b) their energies are the same
(c) energy of A1 is less than the energy of A2
(d) energy of A1 is more than the energy of A2

A, C

Question. If an electron and a photon propagate in the form of waves having same wavelength, it implies that they have same:
(a) speed
(b) momentum
(c) energy
(d) all the above

B

Question. According to Einstein’s photoelectric equation, the graph between the kinetic energy of photoelectrons ejected and the frequency of incident radiation is

D

Question. In which of the following, emission of electrons does not take place?
(a) Thermionic emission
(b) X-rays emission
(c) Photoelectric emission
(d) Secondary emission

B

Question. The work-function of a surface of a photosensitive material is 6.2 eV. The wavelength of incident radiation for which the stopping potential is 5 V lies in:
(a) ultraviolet region
(b) visible region
(c) infrared region
(d) X-ray region

A

Question. In Davison-Germer experiment, an electron beam is incident on a crystal. The reflected beam consists of
(a) photons
(b) protons
(c) x-rays
(d) electrons

D

Question. Photoelectric effect is the phenomenon in which
(a) photons come out of a metal when it is hit by a beam of electrons.
(b) photons come out of the nucleus of an atom under the action of an electric field.
(c) electrons come out of a metal with a constant velocity which depends on the frequency and intensity of incident light wave.
(d) electons come out of a metal with different velocities not greater than a certain value which depends only on the frequency of the incident light wave and not on its intensity.

D

Question. The momentum of a photon of wavelength l is
(a) hλ
(b) h/λ
(c) λ/h
(d) h/cλ

B

Question. A proton, a neutron, an electron and an a-particle have same energy. Then their de Broglie wavelengths compare as
(a) λP = λN > λe > λa
(b) λa < λp = λn > λe
(c) λe < λp = λn > λa
(d) λe = λp = λn = λa

B

Question. In the Davisson and Germer experiment, the velocity of electrons emitted from the electron gun can be increased by
(a) increasing the potential difference between the anode and filament
(b) increasing the filament current
(c) decreasing the filament current
(d) decreasing the potential difference between the anode and filament

A

Question. An electron is accelerated by a p.d. of 1000 V. Its velocity will be
(a) 3.78 × 107 m/s
(b) 1.89 × 107 m/s
(c) 5.67 × 107 m/s
(d) 0.95 × 107 m/s

B

Question. The velocity of a body of rest mass mo is (√3/2)c (where c is the velocity of light in vacuum). The mass of this body is:

D

Question. The maximum kinetic energy (Emax) of photoelectrons emitted in a photoelectric cell varies with frequency (n) as shown in the graph. The slope of the graph is equal to

(a) charge of the electron
(b) e/m of the electron
(c) work function of the emitter
(d) Plank’s constant

D

Question. A photoelectric cell is a device which
(a) converts light into electricity
(b) converts electricity into light
(c) stores light
(d) stores electricity

A

Question. Ultraviolet radiation of 6.2 eV falls on an aluminium surface (work function 4.2 eV). The kinetic energy in joule of the faster electron emitted is approximately
(a) 3 × 10–21
(b) 3 × 10–19
(c) 3 × 10–17
(d) 3 × 10–15

B

Question. The de-Broglie wavelength of a proton (mass = 1.6 × 10–27 kg) accelerated through a potential difference of 1 kV is
(a) 600 A
(b) 0.9 × 10–12m
(c) 7 Å
(d) 0.9 nm.

B

Question. A photocell is illuminated by a small bright source placed 1 m away. When the same source of light is placed 2 m away, the number of electrons emitted by photocathode are reduced by a factor of
(a) 1/8
(b) 1/16
(c) 1/2
(d) 1/4

D

Question. An electron of mass m and charge e initially at rest gets accelerated by a constant electric field E. The rate of change of de-Broglie wavelength of this electron at time t ignoring relativistic effects is

A

Question. The wavelength of Kα-line characteristic X-rays emitted by an element is 0.32 Å. The wavelength of Kβ-line emitted by the same element will be
(a) 0.32 Å
(b) 0.39 Å
(c) 0.49 Å
(d) 0.27 Å

D

Question. Radiations of two photon’s energy, twice and ten times the work function of metal are incident on the metal surface successsively. The ratio of maximum velocities of photoelectrons emitted in two cases is
(a) 1 : 2
(b) 1 : 3
(c) 1 : 4
(d) 1 : 1

B

Question. The X-rays of wavelength 0.5 Å are scattered by a target. What will be the energy of incident X-rays, if these are scattered at an angle of 72º ?
(a) 12.41 keV
(b) 6.2 keV
(c) 18.6 keV
(d) 24.82 keV

D

Question. The momentum of photon whose frequency f is
(a) hf/c
(b) hc/f
(c) h/f
(d) c/hf

A

Question. Which one of the following graphs represents the variation of maximum kinetic energy (EK) of the emitted electrons with frequency u in photoelectric effect correctly ?

D

Question. An ionisation chamber, with parallel conducting plates as anode and cathodes has singly charged positive ions per cm3. The electrons are moving toward the anode with velocity 0.4 m/s. The current density from anode to cathode is X104 m A/m2. The velocity of positive ions moving towards cathode is
(a) 0.1 m/s
(b) 0.4 m/s
(c) zero
(d) 1.6 m/s

A

Question. A light having wavelength 300 nm fall on a metal surface. The work function of metal is 2.54 eV, what is stopping potential ?
(a) 2.3 V
(b) 2.59 V
(c) 1.59 V
(d) 1.29 V

C

Question. 4eV is the energy of incident photon and the work function is 2eV. The stopping potential will be
(a) 2V
(b) 4V
(c ) 6 V
(d) 2 √2V

A

Question. A and B are two metals with threshold frequencies 1.8 × 1014 Hz and 2.2 × 1014 Hz. Two identical photons of energy 0.825 eV each are incident on them. Then photoelectrons are emitted in (Take h = 6.6 × 10–34 Js)
(a) B alone
(b) A alone
(c) neither A nor B
(d) both A and B.

B

Question. A parallel beam of light is incident normally on a plane surface absorbing 40% of the light and reflecting the rest. If the incident beam carries 60 watt of power, the force exerted by it on the surface is
(a) 3.2 × 10–8 N
(b) 3.2 × 10–7 N
(c) 5.12 × 10–7 N
(d) 5.12 × 10–8 N

B

Question. The photoelectric threshold of Tungsten is 2300Å. The energy of the electrons ejected from the surface by ultraviolet light of wavelength 1800Å is
(a) 0.15 eV
(b) 1.5 eV
(c) 15 eV
(d) 150 eV

A

Question. Which of the following when falls on a metal will emit photoelectrons ?
(d) Microwaves

A

Question. The kinetic energy of electron (in electron volt) moving with a velocity of 4 × 106 m/s will be
(a) 60 eV
(b) 50 eV
(c) 30 eV
(d) 45.5 eV

D

Question. Electrons used in an electron microscope are accelerated by a voltage of 25 kV. If the voltage is increased to 100 kV then the de-Broglie wavelength associated with the electrons would
(a) increase by 2 times
(b) decrease by 2 times
(c) decrease by 4 times
(d) increase by 4 times

B

Question. In a photoelectric experiment, the stopping- potential for the incident light of wavelength 4000 Å is 2 volt. If the wavelength be changed to 3000 Å, the stopping-potential will be:
(a) 2 volt
(b) less than 2 volt
(c) zero
(d) more than 2 volt.

D

Question. A photo sensitive metal is not emitting photo-electrons when irradiated. It will do so when threshold is crossed. To cross the threshold we need to increase
(a) intensity
(b) frequency
(c) wavelength
(d) None of these

B

Question. A particle with rest mass m0 is moving with speed of light c. The de-Broglie wavelength associated with it will be
(a) ∝
(b) zero
(c) m0 c/h
(d) hn/m0c

B

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

A

Question. Einstein’s photoelectric equation is Ek = hn – f . In this equation Ek refers to
(a) kinetic energy of all the emitted electrons
(b) mean kinetic energy of emitted electrons
(c) maximum kinetic energy of emitted electrons
(d) minimum kinetic energy of emitted electrons

C

#### Fill in the Blanks [1 mark]

Question. _______________ is a physical quantity whose dimensions are the same as that of Plank’s constant.

Angular momentum

Question. The frequency spectrum of radiation emitted as per Rutherford’s model of atom is _____________.

continuous

Question. According to de Broglie a stationary orbit is that which contains an _______________ number of de Broglie waves associated with the revolting electron.

integral

Question. The value of Rydberg constant is _________________.

1.09 × 107 m–1

Question. The angle of scattering q for zero value of impact parameter b is _________________.

180°

Question. _______________ series of hydrogen spectrum lies in the visible region electromagnetic spectrum.

Balmer

Question. The force responsible for scattering of alpha particle with target nucleus is _______________.

electrostatic force

Question. _______________ is the ionisation potential of hydrogen atom.

13.6 eV

Question. When an electron jumps from 2nd stationary orbit of hydrogen atom to 1st stationary orbit, the energy emitted is _________________.

10.2 eV

Question. Total energy of electron in a stationary orbit is _________________, which means the electron is bound to the nucleus and is not free to leave it.