Matter & Atoms

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

  1. 220 nm
  2. 310 nm
  3. 400 nm
  4. 540 nm

Answer

φ0 = 4 eV

Threshold wavelength

λ = hc/φ0

= 1242/4 nm

= 310 nm

The correct option is B.