A monochromatic beam of light passes from a denser medium into a rarer medium. As a result

Options

A. (a) Its velocity increases
B. (b) Its velocity decreases
C. (c) Its frequency decreases
D. (d) Its wavelength decreases

Explanation

**Step-by-Step Solution:**

1. **Understanding the Mediums:**
- A monochromatic beam of light is traveling from a denser medium to a rarer medium.
- Denser medium has a higher refractive index (μ) compared to the rarer medium.

2. **Refractive Index Definition:**
- The refractive index (μ) of a medium is defined as the ratio of the speed of light in vacuum (c) to the speed of light in that medium (v):
\[ \mu = \frac{c}{v} \]

3. **Comparing Refractive Indices:**
- Since the denser medium has a higher refractive index (μ_d > μ_r), it can be inferred that the speed of light in the denser medium (v_d) is less than the speed of light in the rarer medium (v_r):
\[ v_d < v_r \]

4. **Effect on Velocity:**
- When light transitions from the denser medium to the rarer medium, its speed increases. This is a fundamental property of light: it travels slower in denser media and faster in rarer media.

5. **Conclusion:**
- Therefore, as a result of the transition from a denser medium to a rarer medium, the velocity of the light beam increases.

**Final Answer:**
- The velocity of the monochromatic beam of light increases when it passes from a denser medium to a rarer medium.

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