Question

The figure shows the vertical interface between two transparent materials with different indices of refraction. You do not know the exact value of for each material, but you are told that total internal reflection is possible for light rays incident on the interface from the right side.

Given this information, which of the numbered rays is a possible refracted ray for the incident ray shown?

Answer 1

Answer: Numbered 5 is possible refracted ray for the incident ray shown.

Reason and explaination:

Since it is stated that total internal reflection is possible for light ray incident from right side on the interface. It means right side medium is denser with respect to left side, as total internal reflection takes place when ray is incident from denser medium to rarer. When ray is incident from denser to rarer then ray bend away from normal and then if we increase the angle of incidence then , at a particular value of angle of incidence the angle of refraction is 90⁰. This angle of refraction is called critical angle. When ray is incident more that critical angle then ray reflects back to same medium.

Since it is decided now that right side medium is denser so it is clear now that when incident ray is from left means ray is incident from rarer to denser, hence it will bend towards the normal. Ray numbered 5 is the refracted ray in this case for the incident shown.