Question

On the basis of their experiment, To trace the path of a ray of light through a rectangular glass slab, “students of a class arrived at which one of the following conclusions:
A. Angle of incidence is greater than the angle of emergence.
B. Angle of emergence is smaller than the angle of refraction.
C. Emergent ray is parallel to the refracted ray.
D. Incident ray and emergent ray are parallel to each other.

Answer 1

Hint:Assuming the experiment was taken such that, medium for incident ray and emergent ray are same i.e; there is no change in the medium on both sides of the glass slabs then angle of incidence will be same as angle of emergence.

Complete answer:
We know that for a light ray passing through two different media .Ratio of sine of angle of incidence and sine of angle of refraction is constant .So If there is no change in the medium in the both sides of the glass slab then angle of incidence will be same as angle of emergence. We can also prove it by principle of irreversibility (if light travels from a point A to a point B over a particular path, it can travel over the same path from B to A).

Let's say angle of incidence is i and angle of emergence is e then while reversing the same ray angle of incidence will be e and angle of emergence will be i since both these conditions are ideally same i must be equal to e or angle of incidence must be equal to angle of emergence.In other words incident ray must be parallel to the emergent ray

Hence, Option D is the correct answer.

Note:Here we may be confused between the emergent ray, incident ray and refracted ray. If the medium varies, as the light travels from the air to the window, so does the transition in the direction of light. This is called the beam that's refracted. This ray of light is called the emerging ray, which travels from the denser medium to the rarer medium. An incident angle is called the angle at which the incident ray travels through the surface of the prism to the normal and an emergent angle is called the angle by which the ray escapes from the prism to the normal.