Question

One type of sunburn occurs on exposure to UV light wavelength in the vicinity of 325nm.
How many photons are in 1.00 mJ burst of this radiation?

Answer 1

E = hc/lambda
h = Planck's constant = 6.626 x 10^-34 J*s.
c is speed of light = 3 x 10^8 m/s.
lambda is 325 nm. Put this in meters.
E = Joules for 1 photon = xx.
Then (xxJ/1 photon) = (1.00 mJ/?)
Solve for ?. Be sure and put 1.00 mJ in as J.

Answer 2

1.64*10^15