What happen when Ray of light passes through prism at 90°.

Dear Student

Here I assume that you are asking what happens to a light ray if it is incident normally on the prism.

The incident ray will pass through the incident face of the prism without any deviation.

The angle of emergence of the ray depends on the inclination of the opposite face with respect to the incident face. Let that angle be θ(𝜃<90).The light ray will therefore make an angle of θwith the normal of the opposite face.

According to Snell’s law,

sin𝑖/sin𝑟=𝜇sin⁡i/sin⁡r=μ

Here iis the angle of incidence, ris the angle of refraction and μis the ratio of the refractive indices of the air and prism.

For the opposite face, i=θ and𝜇 should be known.

Putting it in the equation we get angle of emergence as r=sin inverse(sinθ/μ).

Thanks