Question

Light coming from a discharge tube filled with hydrogen falls on the cathode of the photoelectric cell. The work function of the surface of cathode is 4eV. One of the following values of anode voltage (in V) with respect to cathode which will make the photo-current zero is :

• A. -4
• B. -6
• C. -8
• D. -10

Answer 1

The correct option is D -10

Given,

Work function, $\varphi =4eV$

for Hydrogen atom, it can provide a max of 13.6 eV of energy by exciting its electron.

$\therefore$ e(Stopping potential) $\ge$ 13.6 - 4
$\ge$ 9.6

i.e. V = 10 V will make photo current zero.