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Find the wavelength and frequency of a 1 keV photon.




2. Light of wavelength  = 5893 Å is incident on a potassium surface. The stopping potential for the emitted electrons is 0.36 volt. Calculate the maximum energy of the photoelectron, the work function, and the threshold frequency.




3. A 75-W light source consumes 75-W of electrical power. Assume all this energy goes into emitted light of wavelength 600 nm.
(a) Calculate the frequency of the emitted light.
(b) How many photons per second does the source emit?
(c) Are the answers to part (a) and (b) the same? Is the frequency of the light the same thing as the number of photons emitted per second? Explain.