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## Homework Statement

An LED emits a light beam with a power of 10 mW. The wavelength of the light is 420 nm. How many 420nm photons are emitted per sec.?

## Homework Equations

E=hc/lamda is 2.95E-9

P/E= Photons emitted per sec.

(10*10E-3)(2.95E-9)=2.952E-11

## The Attempt at a Solution

2.95E-11 is wrong.

2.1E16 photons per/sec. is the answer