Question

Complete the following: When a ray of light passes from a denser to a rarer medium, its wavelength __________.

• A. decreases
• B. increases

Hint:

Frequency is the "DNA" of a wave; it never changes when the medium changes. Speed and wavelength change together. Denser to Rarer: Speed and Wavelength both INcrease.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Refraction occurs because light travels at different speeds in different media. The frequency of light remains constant when it changes media.
Step 2: Key Formula or Approach:
The relationship between speed (\( v \)), frequency (\( f \)), and wavelength (\( \lambda \)) is given by:
\[ v = f \cdot \lambda \]
Step 3: Detailed Explanation:
When light travels from a denser medium (like glass) to a rarer medium (like air), its speed increases (\( v_{rarer}>v_{denser} \)).
Since frequency (\( f \)) is a characteristic of the source and remains unchanged during refraction:
\[ \lambda \propto v \]
An increase in speed directly leads to an increase in the wavelength of the light ray.
Step 4: Final Answer:
Its wavelength increases.