Question

The potential difference that must be applied to stop the fastest photoelectrons emitted by a nickel surface, having work function 5.01 eV, when ultraviolet light of 200nm falls on it, must be

• A. 2.4V
• B. 1.2V
• C. -1.2V
• D. -2.4V

Answer 1

The correct option is B 1.2V

Work function of metal surface $\varphi =5.01eV$
Wavelength of incident photon $\lambda =200nm$
Energy of incident photon $E=\frac{1240}{\lambda \left(innm\right)}eV=\frac{1240}{200}=6.21eV$
Stopping potential $e{V}_o=E-\varphi$
$\therefore e{V}_o=6.21-5.01=1.2eV$
$⟹V_o=1.2V$