Question

The work function of a substance is 4.0 eV. The longest wavelength of light that can cause photoelectron emission from this substance is approximately

• A. 540 nm
• B. 400 nm
• C. 310 nm
• D. 220 nm

Answer 1

The correct option is C 310 nm

By using ${\lambda }_0=\frac{12375}{W_0\left(eV\right)}\Rightarrow {\lambda }_0=\frac{12375}{4}=3093.7\stackrel{\circ }{A}\simeq 310nm$