Question

Photons with energy $5ev$ are incident on a cathode $C$ in a photoelectric cell. The maximum energy of emitted photoelectrons is $2eV.$ When photons of energy $6eV$ are incident on $C,$ no photoelectrons will reach the anode A. If the stopping potential of $A$ relative to $C$ is

• A. $+3V$
• B. $+4V$
• C. $-1V$
• D. $-3V$

Answer 1

The correct option is D $-3V$

Energy of photons is $5eV$ and maximum energy of the emitted photo electrons is $2eV$.

we get,

$\varphi =K_{max}-E_p$

$\therefore \varphi =5-2=3eV$

Now, when photons of energy $6eV$ are incident. no. photo electrons are emitted .

This is because a stopping potential is applied.

$\therefore e{V}_0=E_p-\varphi =6-3=3eV$

$\therefore V_0=3V$

Hence, a stopping potential of $3V$ has to be applied.

Hence stopping potential of A w.r.t C is $-3V$

So, the correct option $D$