Light of wavelength 5000 Å falls on a plane reflecting surface. What are the wavelength and frequency of the reflected light ? For what angle of incidence is the reflected ray normal to the incident ray ?

Explanation

Here `lamda=5000` Å`=5000xx10^(-10)m=5xx10^(-7)m`
`therefore` Wavelength of reflected light=Wavelength of incident light `lamda=5xx10^(-7)m`
Frequency of reflected light `v=(c)/(lamda)=(3xx10^(8))/(5xx10^(-7))=6xx10^(14)Hz`
As reflected ray is normal to incident ray, hence `anglei+angler=90^(@)` but `angler=anglei`
`therefore anglei+anglei=2anglei=90^(@)impliesanglei=45^(@)`.