Question

When the angle of incidence is 90 degree what is the angle of refraction

Answer 1

Hence resulting in 0° as angle of refraction. If the incident ray is perpendicular, and the angle of incidence is 90° , then the light ray will pass undeviated. So the angle of refraction would be 0° as there is no refraction of light ray, but when measured with respect to normal, the angle would be of measure 90°.