Two answers required. One of these particles imparts energy to multiple instances of the other in a process similar to singlet fission in pentacenes. One of these particles produces multiple instances of the other as it travels through a quantum well heterostructure in a QCL. The rate of conversion between these two particles is measured by the external quantum efficiency. Signal from one of these particles is amplified by triggering a cascade of the other in a (*) PMT. One of these particles is emitted when the other undergoes carrier recombination with a positively-charged counterpart in an LED. “h-nu minus the workfunction” gives the kinetic energy of one of these particles that is (10[1])ejected from a metal when struck by the other. For 10 points, name these two particles: the quanta of light and the negative charge carrier in a solid. ■END■