Question

A parallel beam of monochromatic light of wavelength 663 nm is incident on a totally reflecting plane mirror. The angle of incidence is `60^@` and the number of photons striking the mirror per second is `(1.0 xx (10^19))`. Calculate the force exerted by the light beam on the mirror.

Answer 1

`lamdaxx663xx10^(-9)`m,`theta=60^circ`,`n=1.0xx10^(19)`
`P=(h)/(lamda)-(6.63xx10^(-34))/(6.63xx10^(-9))=10^(-27)`
Force exerted on the wall is `nxx2xxPcostheta=2xx1xx10^(19)xx10^(-27)xx(1)/(2)`
`=1xx10^(-8)N`