Chapter 6, Problem 80QAP

In the photoelectric effect, electrons are ejected from a metal surface when light strikes it. A certain minimum energy, E_min, is required to eject an electron. Any energy absorbed beyond that minimum gives kinetic energy to the electron. It is found that when light at a wavelength of 540 nm falls on a cesium surface, an electron is ejected with a kinetic energy of $2.60\times {10}^{-20}\text{J}$. When the wavelength is 400 nm, the kinetic energy is $1.54\times {10}^{-19}\text{J}$.

(a) Calculate E_min for cesium in joules.

(b) Calculate the longest wavelength, in nanometers, that will eject electrons from cesium.