A photodetector uses a material whose work function is 4.0 eV

PHYSICS · Subjective · A Level · Physics · Particles and radiation · Particles and radiation

Problem

A photodetector uses a material whose work function is 4.0 eV. The device requires the emitted electrons to reach a speed of

7.0\times10^{5}\,\text{m/s}

. Determine the longest wavelength of light that will satisfy this performance specification.