A minimum energy of 7.21⨉10^-19 J is required to produce the photoelectric effect in chromium metal. (b) Light with a wavelength of 2.50⨉10^-7 m falls on a piece of chromium in an evacuated glass tube. What is the minimum de Broglie wavelength of the emitted electrons? (Note that the energy of the incident light must be conserved; that is, the photon's energy must equal the sum of the energy needed to eject the electron plus the kinetic energy of the electron.)