Question

The photon electric threshold of Tungsten is $2300A^o$. The energy of the electrons ejected from the surface by ultraviolet light of wavelength $1800A^o$ is

• A. 0.15 eV
• B. 1.5 eV
• C. 15 eV
• D. 150 eV

Answer 1

The correct option is B 1.5 eV

$E_k=\frac{hc}{c}(\frac{1}{\lambda }-\frac{1}{{\lambda }_0})$ (in eV)
$=\frac{6.6\times {10}^{-34}\times 3\times {10}^8}{1.6\times {10}^{-19}}(\frac{{10}^{10}}{1800}-\frac{{10}^{10}}{2300})=1.5eV$