a ray of light falls on a glass slab of refractive index u.if the reflected and refracted rays are mutually perpendicular to each other,find the angle of incidence.

let i be angle of incidence then angle of reflection is i ,by snell law sin i=usin r

90-i+90-r=90

i+r=90

putting in above eqn.

u=

 tan i

Please find the answer in the attached file