Question

Ejection of the photoelectron from metal in the photoelectric effect experiment can be stopped by applying $0.5V$ when the radiation of $250nm$ is used. The work function of the metal is:

• A. $5.5eV$
• B. $4eV$
• C. $5eV$
• D. $4.5eV$

Answer 1

Answer: (D)

$4.5eV$

From Ejection photoelectron

$\because hv=h{v}_o+K.E.$

$\frac{hv}{x}=\varphi +\text{Stopping pot}$

$\therefore \varphi =\frac{hc}{x}-S.P.$

$=\frac{6.6\times {10}^{-34}\times 3\times {10}^8}{250\times {10}^{-9}\times 1.6\times {10}^{-19}}-0.5\times 1.6\times {10}^{-10}$

$=\frac{6.6\times 3}{250\times 1.6}\times {10}^2-0.5$

$=4.95-0.5$

$\sim 4.5eV$