Question

If refracted ray is at the boundary what is the measurement of the angle of reflection??

Answer 1

if the refracted ray is at the boundary,,,then then ray has not reflected,,because in this case the angle of reflection is not equal to the angle incidence,,,so a minimial increment will result in the reflection of the ray..

Answer 2

if the incident ray is getting partially reflected (along with reflection) ,then it will be reflected at "critical angle" which is fixed for a given pair of media and depends on their refractive indices.