Question

If a ray of light strikes the surface of separation at ______________ degrees, the ray goes undeviated.

Answer 1

1. When the ray of light strikes normally, its angle of incidence is $Zero\left(0\right)$ and hence the angle of refraction will also be $Zero\left(0\right)$ i.e. no deviation.

Hence, If a ray of light strikes the surface of separation at $Zero\left(0\right)$ degrees, the ray goes without any deviation.