Two monochromatic beam A and B of equal intensity I, hit a screen. The number of photons hitting the screen by beam A is twice that by beam B. Then what inference can you make about their frequencies?

Explanation

Suppose `n_(A)` is the number of photons falling per second of beam A and `n_(B)` is the number of photons falling per sencond of beam B.
Thus `" "n_(A)-2n_(B)`
`{:("Energy of falling photon of beam", A= hv _(A)),("Energy of falling photon of beam", B= hv_(B)):}`
Now, according to question,
`therefore" ""intensity of A = intensity of B"`
`" "n_(A)hv_(A)=n_(B)hv_(B)`
`implies" "(v_(A))/(v_(B))=(n_(B))/(n_(A))=(n_(B))/(2n_(B))=1/2`
`implies" "v_(B)=2v_(A)`
Thus, from this relation we can infer that frequency of beam B is twice of beam A.