A light-emitting diode is in an electric circuit with a 12 V power source and a 270-Ohm series resistor. Find: 1) The cu

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A light-emitting diode is in an electric circuit with a 12 V
power source and a 270-Ohm series resistor. Find:
1) The current through the diode;
2) The number of photons per second emitted in the diode;
3) The emitted light power.
Consider the following cases:
a) GaAs: internal efficiency 60%, external efficiency 1.4%.
b) Al0.3Ga0.7As: internal efficiency 20%, external efficiency
1.6%.
c) GaP: internal efficiency 3%, external efficiency 2%.