A monochromatic ray of photons of energy 5 eV are incident on cathode. Electrons reaching the anode have kinetic energyies varying from 6 eV to 8eV.Choose the correct option.

Options

A. work function of the metal is 1 eV
B. work function of the metal is 3 eV
C. current in the circuit is equal to saturation value
D. current in the circuit is less than saturation value.

Answer

D

Explanation

`KE_(max ) = (5 - phi) e V `
when these electrons are accelerated through 5v, they will reach the anode with maximum energy
`= (5 - phi +5 ) e V `
`10 - phi =8 `
`phi = 2eV `
Current is less than saturation current because if slowest electron also reached the plate it would have 5 eV energy at the anode, but there it is given that the minimum energy is 6 eV.