Which is the key step for uniquely defining phosphorescence and fluorescence, and does not occur in other types of emission? Question 4Answer a. the emission of photons continues after a UV source is removed b. an electron drops from a high energy level to a lower energy level, and emits a visible wavelength photon c. absorption of UV photon by an electron, which jumps to a higher energy level d. an electron drops from a high energy level to a slightly lower energy level, and does not emit a visible wavelength photon