Question

1. in quantum mechanical terms, explain why certain leds initiate phosphorescence and others do not. include an explanation of threshold frequency in your answer.

Explanation:

LEDs (Light - Emitting Diodes) initiate due to the quantum - mechanical process of electron - hole recombination in a semiconductor. When an electric current is applied, electrons in the conduction band recombine with holes in the valence band, emitting photons. The energy of the emitted photons corresponds to the band - gap energy of the semiconductor material, which determines the color (frequency) of the light. This process does not involve phosphorescence (a slower light - emission process after excitation) as LEDs are based on spontaneous emission from the recombination of charge carriers in the semiconductor.

Answer:

LEDs initiate due to electron - hole recombination in a semiconductor, emitting photons with energy corresponding to the semiconductor's band - gap, and this is a quantum - mechanical process that does not involve phosphorescence.