Question

In photo electric effect, the work function of a metal is $3.5\text{eV}$. The emitted electrons can be stopped by applying a potential of $-1.2\text{V}$. Then -

• A. the energy of the incident photon is $4.7\text{eV}$.
• B. the energy of the incident photon is $2.3\text{eV}$.
• C. if higher frequency photons be used, the photoelectric current will rise.
• D. when the energy of photons is $3.5\text{eV}$, the photoelectric current will be maximum.

Answer 1

The correct option is A the energy of the incident photon is $4.7\text{eV}$.

From Einstein photoelectric effect equation,

$K{E}_{\text{max}}=h\nu -\varphi$

$\Rightarrow eV=h\nu -\varphi$

$\Rightarrow 1.2=h\nu -3.5$

$\Rightarrow h\nu =4.7\text{eV}=\text{energy of the incident photon}$

Photoelectric current depends on the intensity of radiation, not on frequency or energy of photons.

Hence, option $\left(A\right)$ is the correct answer.