A certain sodium lamp radiates 400 W of yellow light of wave length 5896 Å. Calculate the number of photons emitted by this light in each second `(c = 3 x 10^(8) ms^(-1))`.

Explanation

Given : `lambda = 5.896xx10^(7)` m
Total energy emitted par second E. = 400 W, No. of photons emitted per second n = ?
`P=E/t=(nhv)/t`
`therefore n/t = (Plambda)/(hc), ` where ` v = c/lambda `
`n/t = (400xx5896xx10^(-10))/(6.626xx10^(-34)xx3xx10^(8))=1.186xx10^(21)` photon/s.