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

Explanation

Given, wavelength , `lambda = 5000 Å = 5 xx 10^(-7) m`
The wavelength and frequency of reflected light remains the same.
`:.` Wavelength of reflected light,
`lambda = 5000 Å`
Frequency of reflected light,
`:. v = c/lambda = (3 xx 10^8)/(5 xx 10^(-7)) = 6 xx 10^(14) Hz`
For the reflected ray to be normal to incident ray
`/_i + /_r = 90^@`
As `/_r = /_i`
`2/_i = 90^@`
`implies /_i = 45^@`.