Question

A photon can eject an electron from the surface of a photo-voltaic metal. Identify which of the following is must condition for above statement.

• A. The frequency of the photon is above the activation minimum
• B. The wavelength of the photon is above the activation minimum
• C. The speed of the photon is above the activation minimum
• D. The momentum of the photon is below the activation minimum
• E. The momentum of the impacted electron is above the activation minimum

Answer 1

The correct option is A The frequency of the photon is above the activation minimum

According to Einstein's Photoelectric effect, the maximum kinetic energy of an ejected electron when a photon of energy $h\nu$ strikes a metal of work potential $W_0$ is $KE=h\nu -W_0$

Thus for photoelectric effect to take place,

$KE>0$

$⟹h\nu -W_0>0$

$⟹\nu >\frac{W_0}{h}$