Question

Let a light of wavelength $\lambda$ and intensity '$I$' strikes a metal surface to emit $x$ electrons per second. Average energy of each electron is '$y$' unit. What will happen to '$x$' and '$y$' when (a) $\lambda$ is halved (b) intensity $I$ is doubled?

Answer 1

(a) Rate of emission of electron is independent of wavelength. Hence, '$x$' will be unaffected.
Kinetic energy of photoelectron $=$ Absorbed energy $-$ Threshold energy
$y=\frac{hc}{\lambda }-w_0$
when, $\lambda$ is halved, average energy will increase but it will not become double.
(b) Rate of emission of electron per second '$x$' will become double when intensity $I$ is doubled. Average energy of ejected electron, i.e., '$y$' will be unaffected by increase in the intensity of light.