The human eye receives a 3.65x 10"J signal from photons whose wavelength is of S15 nnm. How many photons strike the eye?

The watt is the derived SI unit of power, the measure of energy per unit time: 1 W=1 J/s.

A semiconductor laser in a CD player has an output wavelength of 780 nm and a power level of 0.10 mW.  How many photons strike the CD surface during the playing of a CD 69 minutes in length?

The human eye can barely detect a star whose intensity at theearth's surface is 1.6\times10^{-11}\;{\rm W/m^{2}}
If the dark adapted eye has a pupil diameter of 6.0 {\rm mm}, howmany photons per second enter the eye from the star? Assume thestarlight has a wavelength of 550 {\rm nm}.