What is a necessary condition for total internal reflection in a medium?
a. when the angle of incidence is equal to the critical angle
b. when the angle of incidence is greater than the critical angle
c. when the angle of refraction is equal to the critical angle
d. when the angle of reflection is less than the critical angle

B. when the angle of incidence is greater than the critical angle

Explanation:

As we know by law of refraction of light that

now here we know that total internal reflection only occurs when light travel from denser medium to rarer medium.

so here

now if angle is critical angle then at that point angle of refraction must be 90 degree

so if angle is more than critical angle then it will always follow the law of reflection so correct answer is

B. when the angle of incidence is greater than the critical angle

this means that the temperature of both substances will be equal