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•• Consider a current of 3 mA flowing through an LED whose band gap is about 2 eV. (a) How many photons are produced per second? (b) What is the power of the light produced? Notice that this small current produces a light that is easily visible. (For comparison, a typical flashlight bulb, which is very easily visible, consumes about a watt of power, of which about 50 mW is visible light.) (c) Show in general that this power (in watts) is numerically just the product of the current (in amperes) and the band gap (in eV).
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