A 100 W point source emits monochromatic light of wavelength `6000 A`
Calculate the total number of photons emitted by the source per second.

Options

A. `5xx10^(20)`
B. `8xx10^(20)`
C. `6xx10^(21)`
D. `3xx10^(20)`

Answer

D

Explanation

Energy of a photon of wavelength `lamda`,
`E=hv=((hc)/(lamda))`
`E=((6.6xx10^(-34))xx(3xx10^(8)))/(6000xx10^(-10))`
`=3.3xx10^(-19)J`
So, if n is the number of photons emitted per second,
`nE=("energy")/("second")="power"(P)`
Hence, `n=(P)/(E)=(100)/(3.3xx10^(-19))`
`approx3xx10^(20)`, photons `s^(-1)`