hello aspirant
When the angle of incidence for a prism is 90 degree then the ray just grazes along the surface of the prism . This is known as grazing incidence and in this case the angle of refraction at the first refracting surface is equal to the critical angle of the material of the prism.
hope this helps
Eligibility | Application | Exam Pattern | Admit Card | Preparation Tips | Result | Answer Key
Regular exam updates, QnA, Predictors, College Applications & E-books now on your Mobile