Monochromatic light of frequency `6xx10^(14)Hz` is produced by a laser. The power emitted is `2xx10^(-3)` W.
The number of photons emitted per second is
`("Given h"=6.63xx10^(-34)Js)`

Options

A. `6 xx 10^(14)`
B. `4 xx 10^(15)`
C. `2 xx 10^(16)`
D. `1 xx 10^(17)`

Answer

C

Explanation

Energy of a photon, `E=h epsilon`
`E = (6.63 xx 10^(-34) Js)(6 xx 10^(14)Hz)= 39.8 xx 10^(-20)` J
Power of the source, `P=8 xx 10^(-3) W`
Number of photons emitted per second is
`N= P/E = (8 xx 10^(-3)W)/(39.8 xx 10^(-20)) J = 2 xx 10^(16)`