Question

A light of wavelength $310nm$ is used in a photoelectric experiment. The metal electrode of work function of $2.5eV$ is used in the experiment. The stopping potential for the photoelectrons will be(Assume $hc=1240eV-nm$)

• A. 1.0 V
• B. 1.5 V
• C. 2.0 V
• D. 2.5 V

Answer 1

Answer: (B)

Work-function of metal surface, ${\phi }_0=25eV$
Wavelength, $\lambda =310nm$
$\Rightarrow hc=1240eV-nm$
According to Einstein's photoelectric equation,
$e{V}_0=\frac{hc}{\lambda }-{\phi }_0$
$\Rightarrow e{V}_0=\frac{1240eV-nm}{310nm}-2.5eV$
$\Rightarrow V_0=\frac{1240}{310}-25=4-25=1.5V$