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:

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

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?

Frequently Asked Questions

What scientific concept do you need to know in order to solve this problem?

Our tutors have indicated that to solve this problem you will need to apply the Energy Carried by Electromagnetic Waves concept. You can view video lessons to learn Energy Carried by Electromagnetic Waves. Or if you need more Energy Carried by Electromagnetic Waves practice, you can also practice Energy Carried by Electromagnetic Waves practice problems.