Question

Threshold wavelength of tungsten is 2300 angstrom. If ultraviolet light of wavelength 1800 angstrom is incident on it, then the maximum kinetic energy of photoelectrons would be ?

• A. 1.5 eV
• B. 2.5eV
• C. 3.0 eV
• D. 5.0eV

Answer 1

The correct option is A 1.5 eV

$k_{max}=hv-h{v}_o$

$=hc(\frac{1}{\lambda }-\frac{1}{\lambda })$

$=1.24\times {10}^{-6}(\frac{{10}^8}{18}-\frac{{10}^8}{23})$

$k_{max}=1.489eV$

$k_{max}\approx 1.5ev$

Hence option A is correct.