Question

When light is incident on surface, photo electrons are emitted. For photoelectrons:

• A. The value of kinetic energy is same for all
• B. Maximum kinetic energy do not depend on the
  wave length of incident light
• C. The value of kinetic energy is equal to or less
  than a maximum kinetic energy
• D. None of the above

Answer 1

Answer: (C)

The value of kinetic energy is equal to or less

than a maximum kinetic energy

Kinetic energy of photo electron is

KE = hf - W = $\frac{hc}{\lambda }$ - W

h = plancks constant

f = frequency

$\lambda$= wavelength of incident light

W = work function

The photo electrons are not emitted instantly. They collide several times with other electrons within the metal before coming out. Hence the value of kinetic energy is not the same. From above equation, Kinetic energy depends on wavelength of incident light.Also the value of kinetic energy is less than or equal to $hf$

$Hence,\; Option\; (B)\; is\; correct$