Question

The photoelectric threshold wavelength for potassium (work function being 2 eV) is

• A. 310 nm
• B. 620 nm
• C. 1200 nm
• D. 2100 nm

Answer 1

The correct option is B 620 nm

$\varphi =\frac{hc}{\lambda t}$

2eV=$\frac{1240}{\lambda T}eV-nm$ (hc=1240 eV-nm)

${\lambda }_T=\frac{1240}{2}nm$

=620nm

So, the answer is option (B).