Question

A ray of light at an angle of incidence 60 degrees on a refracted surface.If the reflected and refracted rays are perpendicular to each other, what is the refractive index of the medium ?

Answer 1

 sketch the diagram yourself . u will find 
i + r = 90°
now refractive index of the medium 
μ = sini/sinr
  =  sini/sin(90° - i)         as i + r = 90°
  = sini/cosi
  = tani
and as i = 60° so μ = tani = tan 60° = √3