Light Refraction and Wavelength/Color – Rankers Physics

Refraction by Plane Surfaces: Practice Problem & Solution

Assertion (A): Light of wavelength \(5500 \text  A^0\) travelling in medium 1 is incident on an interface and gets refracted into medium 2. Due to refraction, if it deviates by an angle \(15^{\circ}\), then its wavelength in medium 2 could be greater than or smaller than \(5500 \text{ A^0}\) but never the same. Reason (R): As light is refracted, its colour changes.  
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:

During refraction, the frequency of light remains constant, which means its color does not change. However, its wavelength \(\lambda\) and speed \(v\) change such that \(n_1\lambda_1 = n_2\lambda_2\). Since the light deviates, \(n_1 \neq n_2\), implying \(\lambda_1 \neq \lambda_2\). Thus, Assertion (A) is true and Reason (R) is false.

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