Question

For intensity $I$ of a light of wavelength $5000\mathring{A}$ the photoelectron saturation current is $0.40\mu A$ and stopping potential is $1.36V$, the work function of metal is :

• A. 1.36 eV
• B. 1.10 eV
• C. 2.47 eV
• D. 0.43 eV

Answer 1

Answer: (B)

Energy due to incoming light is $E=hc/\lambda$ where $h=6.6\times {10}^{-4}$ is the plank's constant, so

$E=6.6\times {10}^{-34}\times 3\times {10}^8/(5000\times {10}^{-10}\times 1.6\times {10}^{-19})eV=2.475eV$

Stopping potential is $1.36eV$

So work function is $W_o=2.475-1.36=1.115eV$