Frequency and Coplanarity of Light Rays – Rankers Physics

Refraction by Plane Surfaces: Practice Problem & Solution

Assertion (A): When a monochromatic beam of light is incident from one medium to another, the frequency of incident, reflected and refracted rays are equal. Reason (R): The incident, reflected and refracted rays are co-planar.  
Both (A) & (R) are true and the (R) is the correct explanation of the (A)
Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
(A) is true but (R) is false
Both (A) and (R) are false

Solution Explained:

To solve this problem, we apply the core principles of Refraction by Plane Surfaces. Understanding the underlying formula is key to arriving at the correct answer below:

The frequency of light is an intrinsic property of the source and remains constant upon changing media, so A is true. According to laws of reflection and refraction, the incident, reflected, and refracted rays lie in the same plane as the normal, so R is true. However, R does not explain A.

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