7. Diodes can emit light. a) In a light emitting diode, what must be done electrically to cause the diode to emit light? How is the light emitted? b) What feature of the band gap is needed to make the LED emit light without much energy going into heat? c) Is the light from an LED produced primarily by spontaneous emission or stimulated emission? What feature of the LED determines the color of the light? e) What addition to an LED is needed to make a laser diode? f) Is the light from a laser diode produced primarily by spontaneous emission or stimulated emission?