Question

Monochromatic light of frequency `6.0xx10^(14)Hz` is produced by a laser. The power emitted is `2.0xx10^-3W`, (a) What is the energy of a photon in the light beam? (b) How many photons per second, on the average, are emitted by the source? Given `h=6.63xx10^(-34) Js`

Answer 1

(a) `E=hv`
`=6.63xx10^(-34)xx6.0xx10^(14)`
`=3.98xx10^(-19)J=(3.98xx10^(-19))/(1.6xx10^(-19))=2.49eV`
(b) No. of photons emitted per second,
`n=P/E=(2.0xx10^-3W)/(3.98xx10^(-19)J)`
`=5.0xx10^(15)` photons per second