A monochromatic source , emitting light of wavelength , 600 nm , has a power output of 66 W. Calculate the number of photons emitted by this source in 2 minutes.

Asked by vinitapahel123 | 13th Dec, 2015, 12:04: PM

Expert Answer:

Given:
Wavelength, λ = 600nm = 6×10-7 m
Power, P = 66 W
Energy of one photon, E = begin mathsize 14px style hc over straight lambda end style
begin mathsize 14px style straight E equals hc over straight lambda equals fraction numerator left parenthesis 6.6 cross times 10 to the power of negative 34 end exponent right parenthesis cross times left parenthesis 3 cross times 10 to the power of 8 right parenthesis over denominator 6 cross times 10 to the power of negative 7 end exponent end fraction equals 3.3 cross times 10 to the power of negative 19 end exponent space straight J end style
Let n is the number of photons emitted per second such that the energy emitted in one second is 66 J.
begin mathsize 14px style therefore end stylenE = 66
begin mathsize 14px style straight n equals 66 over straight E equals fraction numerator 66 over denominator 3.3 cross times 10 to the power of negative 19 end exponent end fraction equals 1.99 cross times 10 to the power of 20 space photons divided by sec end style
Total number of photons emitted by source in 2 mins = n × 2 × 60 = 2.388 × 1022 photons.   [2 mins = 2 × 60]

Answered by Faiza Lambe | 13th Dec, 2015, 03:41: PM