Question

A light source, of power P, gives x⁰/0 of its emitted energy, in the form of a monochromatic radiation of wavelength λ. This wavelength is less than the threshold wavelength (λ₀) of a given photosensitive material.

A circular lamina, of radius r, (made from this given photosensitive material) is kept at a distance d from the given light source. Assuming each incident photon (of radiation of wavelengTh λ), to cause the emission of one photoelectron, the total charge Q, carried by all the photoelectrons, emitted in t seconds, is

Answer 1

Correct option : (1)

Explanation: 

The power, associated with the radiation of wavelength λ, equals 

Energy of one photon = hv/λ

. ^.. Number of photons emitted per second 

At a distance d, the number of these photons, per unit area, is

 

Hence the number of photons, striking the circular lamina, in one second, is

In a time of t seconds, the number of emitted photoelectrons would be te. The charges carried by them, equals nte. Hence