Refraction by Plane Surfaces: Practice Problem & Solution

Short Solution (Best for NEET):

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:

When light travels from a rarer medium like vacuum to a denser medium, its frequency remains unchanged while its velocity decreases. Since velocity $v = f \lambda$, the wavelength also decreases. Specifically, $\lambda' = \frac{\lambda}{\mu}$, making the new wavelength smaller.