Question

The retarding potential necessary to stop the emission of photoelectrons, when a target material of work function $1.24eV$ is irradiated with light of wavelength $4.36\times 10^{7}m$ is

• A. $4.08eV$
• B. $2.84eV$
• C. $1.60eV$
• D. $0.36eV$

Answer 1

Answer: (C)

Given, work function, ${\phi }_0=1.24eV$
$=1.24\times 1.6\times 10^{-19}J$
Wavelength, $\lambda =4.36\times 10^{-7}m$
According to Einstein's photoelectric equation,
$e{V}_0=\frac{hc}{\lambda }-\phi$
$\Rightarrow e{V}_0=\frac{6.63\times 10^{-34}\times 3\times 10^8}{4.36\times 10^{-7}}-1.24\times 1.6\times 10^{-19}$
$V_0=\frac{6.63\times 10^{-34}\times 3\times 10^8}{1.6\times 10^{-19}\times 4.36\times 10^{-7}}-1.24$
$=2.85-1.24=1.61V\sim eq1.60V$