Question

The work function of nickel is $5eV$. When light of wavelength $2000$$A^0$ falls on it, emits photoelectrons in the circuit. Then the potential difference necessary to stop the fastest electrons emitted is: (Given $h=6.67\times {10}^{-34}$Js)

• A. $1.0V$
• B. $1.75V$
• C. $1.2V$
• D. $0.75V$

Answer 1

Answer: (C)

$1.2V$

Stopping potential $=(\frac{hc}{\lambda }-\varphi )/e$

$=(\frac{1240}{200}-5)/e$ $\because (hc=1240eV-nm)$

$=(6.2-5)eV/e$

$=1.2eV/e$

$=1.2V$