91Ó°ÊÓ

The photoelectric effect is the ejection of surface electrons in a metal when photon strikes. The mathematical expression governing the effect and giving the maximum kinetic energy of the ejected electrons is,

$$\begin{gathered} \mathit{K}\mathbf{.}{\mathit{E}}_{\mathbf{m}\mathbf{a}\mathbf{x}}\mathbf{=}\mathit{h}\mathit{f}\mathbf{-}\mathit{Φ} \\ \mathit{e}{\mathit{V}}_{\mathbf{0}}\mathbf{=}\mathit{h}\mathit{f}\mathbf{-}\mathit{h}{\mathit{f}}_{\mathbf{0}} \end{gathered}$$ ...(i)

Where $\mathrm{Φ}$the work function, hf is the energy of the striking photon, f₀ is the threshold frequency and V₀ is the stopping potential that reduces the current to zero.

According to equation (i), the maximum kinetic energy of the photoelectron is dependent on the work function of the metal and the frequency of the incident photon. Also the frequency of a photon is given as,

$f=\frac{c}{\mathrm{λ}}$

So, it is dependent on speed of light and inversely dependent on the wavelength. Hence, the maximum kinetic energy can be increased by using a material with different work function and energy of the incident photon, i.e. increasing the frequency and decreasing the wavelength. Thus, the correct option is (b).