PYQ NEET- Dual Nature Of Matter And Radiation L-3

Question: The light rays having photons of energy $4.2 \mathrm{eV}$ are falling on a metal surface having a work function of 2.2 $\mathrm{eV}$. The stopping potential of the surface is#

A) $6.4 \mathrm{~V}$

B) $2 \mathrm{eV}$

C) $2 \mathrm{~V}$

D) $1.1 \mathrm{~V}$

Answer: $2 \mathrm{~V}$#

Solution:#

$$ \begin{aligned} & \text { We know, } K E_{\max }=h v-h v_0 \ & e V_0=h v-h v_0\left(\because K E_{\max }=e V_0\right) \ & e V_0=4.2 \mathrm{eV}-2.2 \mathrm{eV} \ & \therefore V_0=2 \mathrm{~V} \end{aligned} $$