Problem 7 (25 points) Light is incident on the surface of metallic nickel, from which 5.0 ev are required to remove an electron. The stopping potential is 4.5 volts. (Note that I ev = 1.6 x 10-19 J.) (a) Find the wavelength of the incident light. (8 points) (b) Would this light emit any electrons from a metal whose work function is 8.4 ev? If so, determine the maximum kinetic energy of an emitted electron (in either J or eV). If not, explain why. (8 points) (c) If the power of the light source is 2.5 mW, how much time is required for 2.0 x 1017 photons to be emitted by the source, and what is the momentum of each photon? (9 points)