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

## Dual Nature of Radiation and Matter Class 12 MCQs Questions with Answers

Solve this Dual Nature of Radiation and Matter Multiple Choice Questions of Class 12 Physics Chapter 11 MCQ, so as not to miss out on any concept from being clear about what they mean!

Question 1.
When the light of frequency 2v0 (where v0 is threshold frequency) is incident on a metal plate, the maximum velocity of electrons emitted is v1. When the frequency of the incident radiation is increased to 5v0, the maximum velocity of electrons emitted from the same plate is v2. The ratio of v1 to v2 is:
(a) 1 : 2
(b) 1 : 4
(c) 4 : 1
(d) 2 : 1

Question 2.
The wavelength of a photon needed to remove a proton from a nucleus which is bound to the nucleus with 1 MeV energy is nearly
(a) 1.2 nm
(b) 1.2 × 10-3 nm
(c) 1.2 × 10-6 nm
(d) 1.2 × 101 nm

Answer: (b) 1.2 × 10-3 nm

Question 3.
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) λα < λp = λn > λe
(c) λe < λp = λn > λa
(d) λe = λp = λn = λa

Answer: (b) λα < λp = λn > λe

Question 4.
The photoelectric threshold wavelength of silver is 3250 × 10-10 m. The velocity of the electron ejected from a silver surface by ultraviolet light of wavelength 2536 × 10-10 m is:
(Given h = 4.14 × 10-15 eVs and c = 3 × 108 m s-1)
(a) = 0.6 × 105 m s-1
(b) = 61 × 10³ m s-1
(c) = 0.3 × 106 m s-1
(d) = 6 × 105 m s-1

Answer: (d) = 6 × 105 m s-1

Question 5.
An electron beam is accelerated by a potential difference V to hit a metallic target to produce X-rays. It produces continuous as well as characteristic X-rays. If λmin is the smallest possible wavelength of X-ray in the spectrum, the variation of log λmin with log V is correctly represented in:

Question 6.
Photons with energy 5 eV are incident on a cathode C in a photoelectric cell. The maximum energy of emitted photoelectrons is 2 eV. When photons of energy 6 eV are incident on C, no photoelectrons will reach the anode A, if the stopping potential of A relative to C is
(a) – 1 V
(b) – 3 V
(b) + 3 V
(d) + 4 V

Question 7.
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) H°
(d) H-1/2

Question 8.
An electron is moving with an initial velocity $$\vec {v}$$ = v0$$\hat {j}$$ and is in a magnetic field
$$\vec {B}$$ = B0$$\hat {j}$$. Then its de-Broglie wavelength
(a) remains constant
(b) increases with time
(c) decreases with time
(d) increases and decreases periodically

Question 9.
An electron (mass m) with an initial velocity $$\vec {v}$$ = v0$$\hat {j}$$ is in an electric field
$$\vec {E}$$ = E0$$\hat {j}$$. If λ0 = $$\frac { h }{mv_0}$$, its de-Broglie wavelength at time t is given by
(a) λ0
(b) λ0 $$\sqrt{1+\left(\frac{e E_{0} t}{m v_{0}}\right)^{0}}$$
(c) $$\frac{\lambda_{0}}{\sqrt{1+\left(\frac{e E_{0} t^{t}}{m v_{0}}\right)^{2}}}$$
(d) $$\frac{\lambda_{0}}{1+\left(\frac{e E_{0} t}{m v_{0}}\right)^{2}}$$

Answer: (c) $$\frac{\lambda_{0}}{\sqrt{1+\left(\frac{e E_{0} t^{t}}{m v_{0}}\right)^{2}}}$$

II. Fill in the blanks

Question 1.
……………… is the phenomenon of the emission of electrons from a metal surface when radiation of suitable frequency falls on the metal surface.

Question 2.
The phenomenon of emission of electrons from a hot metal surface is called ………………

Question 3.
The minimum energy required by a free electron to just escape from the metal surface is called ………………

Question 4.
This unit of energy commonly used in atomic and nuclear physics is ………………

Question 5.
The work function (Ø0) depends on the properties of the metal and the ……………… of its surface.

Question 6.
……………… is defined as the energy acquired by an electron when it is accelerated through a potential difference of 1 volt.

Question 7.
The energy of the photon is given by ………………

Answer: E = hv = $$\frac { hc }{λ}$$.

Question 8.
The velocity of photon in different media is ………………

Question 9.
The rest mass of a photon is ………………

Question 10.
In a photon-particle collision (such as photon-electron collision), the total ……………… and total momentum are conserved.

Question 11.
The maximum kinetic energy of emitted photoelectrons depends on the ……………… of incident radiation and the nature of material.

Question 12.
The maximum kinetic energy of emitted photoelectrons is independent of ……………… of incident radiation.

Question 13.
The photoelectric current of emitted photoelectrons depends on the ……………… of incident radiation.

Question 14.
The photo-electric current of emitted photoelectrons is independent of the ……………… of incident radiation.

Question 15.
The minimum frequency required to eject an electron from the surface of a metal surface is called ……………… frequency.

Question 16.
For a frequency v of incident radiation, ……………… than the cut-off frequency v0, no photoelectric emission is possible even if the intensity is large.

Question 17.
Photons are electrically ……………… and are not deflected by electric and magnetic fields.

Question 18.
Davison-Germer experiment verified the ……………… nature of moving electrons.

Answer: λ = $$\frac { 1.227 }{√V}$$ nm