Energy Carried by Electromagnetic Waves Video Lessons

Concept

# Problem: A light-emitting diode (LED) connected to a 3.0 V power supply emits 440 nm blue light. The current in the LED is 16mA, and the LED is 71% efficient at converting electric power input into light power output. How many photons per second does the LED emit?

###### FREE Expert Solution

Power and Energy relation:

$\overline{){\mathbf{P}}{\mathbf{=}}\frac{\mathbf{E}}{\mathbf{t}}}$

Electrical power:

$\overline{){\mathbf{P}}{\mathbf{=}}{\mathbf{V}}{\mathbf{i}}}$

The energy carried by electromagnetic wave:

$\overline{){\mathbf{E}}{\mathbf{=}}\frac{\mathbf{h}\mathbf{c}}{\mathbf{\lambda }}}$

Efficiency:

$\overline{){\mathbf{\eta }}{\mathbf{=}}\frac{{\mathbf{P}}_{\mathbf{o}\mathbf{u}\mathbf{t}}}{{\mathbf{P}}_{\mathbf{i}\mathbf{n}}}}$

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###### Problem Details

A light-emitting diode (LED) connected to a 3.0 V power supply emits 440 nm blue light.

The current in the LED is 16mA, and the LED is 71% efficient at converting electric power input into light power output.

How many photons per second does the LED emit?