A ray of light is moving from a rare to a denser medium and strikes a plane mirror at to the direction of the ray as shown in the diagram.

(i). Copy the diagram and mark the arrows to show the path of the ray of the light after it is reflected from the mirror.

(ii). Name the principle you have used to mark the arrow the direction of the ray.

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,principle of reversibility of light

Both a and b

None of these

answer is A.

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Detailed Solution

Concept- It is known that the ray will reflect at

using the law of reflection. So, after reflecting from the mirror, the light will follow the same path back.
Refraction is a phenomenon that happens when the medium through which light travels changes. The optical density of different media varies. Optically, a denser medium has a higher density than a rarer one.
Question Image

Light is seen to bend in the direction of normal when it transitions from a rarer to a denser medium. Light deviates from the usual when it transitions from a denser medium to a rarer media.
The Snell's law describes the relationship between the angles formed as light changes its medium and the respective refractive index:

According to the concept of reversibility, if light travels in the wrong direction, it will follow the same path again. If the course of the light is simply reversed, which can be done by inserting a mirror into the path of the light just perpendicular to its passage, there are no modifications, losses, or further bending. We can infer that the reversibility principle is a straightforward derivation of Snell's law.
As a result, in this instance, the light retraces the precise route as it strikes the mirror at perpendicular angles. Therefore, the reversibility concept has been applied.
Hence, option 1 is correct.

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