A light emitting diode produces light when:Select one:a.an electron undergoes a transition from the valence band to the conduction band.b.an electron decreases its energy when in the valence band.c.an electron undergoes a transition from the conduction band to the valence band.d.an electron increases its energy when in the conduction band.

LEDs (light-emitting diodes) produce light through the recombination of electrons and holes in a semiconductor material when an electrical current is applied.

The light from an OLED device is produced by the:A.excitation of an electron to a higher energy level.B.absorption of a high-energy photon.C.emission of a positron associated with the relaxation of an electron.D.emission of a photon associated with the relaxation of an electron.

Which of the following statement is not correct in the case of light emitting diodes?A. It is a heavily doped p-n junction.B. It emits light only when it is forward biased.C. It emits light only when it is reverse biased.D. The energy of the light emitted is equal to or slightly less than the energy gap of the semiconductor used.Choose the correct answer from the options given below :C and DACB

9. What occurs when an electron moves from high- energy level to alow one?A. The atom moves fasterB. Colored light is given offC. This process is not possibleD. Another electron goes from a low energy level to a high one.

In order to explain the results of a photoelectric effect experiment, quantum physics suggests that:(select all that apply)Question 3Answera.light energy is quantised (in the form of photons)b.electron energies are quantised into levelsc.electrons store the energy from several photons to build up and excite over time.d.electrons can interact with photons only on an all or nothing basise.electrons can absorb any energyf.electrons can only be ejected from a metal with an excess negative charge