41.

Threshold wavelength for photoelectric emission from a metal surface is 5200 $\stackrel{\circ }{\mathrm{A}}$. Photoelectrons will be emitted when this surface is illuminated with monochromatic radiation from

• 1 W IR lamp

• 50 W UV lamp

• 50 W IR lamp

• 10 W IR lamp

From the figure describing photoelectric effect we may infer correctly that

• Na and Al both have the same threshold frequency

• maximum kinetic energy for both the metals depend linearly on the frequency

• the stopping potentials are different for Na and Al for the same change in frequency

• Al is a better photo sensitive material than Na

When light of wavelength 300 nm falls on a photoelectric emitter, photoelectrons are liberated. For another emitter, light of wavelength 600 nm is suffcient for liberating photoelectrons. The ratio of the work function of the two emitters is

• 1 : 2

• 2 : 1

• 4 : 1

• 1 : 4

Maxium velocity of the photoelectrons emitted by a metal surface is 1.2 x 10⁶ ms^-1. Assuming the specific charge of the electron to be 1.8 x 10¹¹ C kg^-1, the value of the stopping potential in volt will be

• 2

• 3

• 4

• 6

Which one of the following graph represents the variation of maximum kinetic energy (E_k) of the emitted electrons with frequency v in photoelectric effect correctly ?

A and B are two metals with threshold frequencies 18 x 10¹⁴ Hz and 2.2 x 10¹⁴ Hz. Two identical photons of energy 0.825 eV each are incident on them. Then photoelectrons are emitted by (Take h = 6.6 x 10^-34 J-s)

• B alone

• A alone

• neither A nor B

• both A and B

The electromagnetic theory of light failed to explain

• photoelectric effect

• polarisation

• diffraction

• interference

When a piece of metal is illuminated by a monochromatic light of wavelength λ, then stopping potential is 3V_s. When same surface is illuminated by light of wavelength 2λ, then stopping potential becomes V_s. The value of threshold wavelength for photoelectric emission will be

• 4λ

• 8λ

• $\frac{4}{3}\mathrm{\lambda }$

• 6λ

The maximum kinetic energy of emitted electrons in a photoelectric effect does not depend upon

• wavelength

• frequency

• intensity

• work function

The amount of energy released when one microgram of matter is annihilated is

• 25 kWh

• 9 × 10¹⁰ kWh

• 3 × 10¹⁰ kWh

• 0.5 × 10⁵ kWh