When a light ray passes from an optically denser medium into an optically rarer medium,

Options

A. its velocity increases
B. frequency requency remains same
C. wavelength increases
D. All the above

Answer

To solve the question regarding the behavior of a light ray when it passes from an optically denser medium to an optically rarer medium, we can break down the explanation into clear steps:

### Step-by-Step Solution:

1. **Understanding the Terms**:
- **Optically Denser Medium**: A medium with a higher refractive index (N1).
- **Optically Rarer Medium**: A medium with a lower refractive index (N2).

2. **Behavior of Light at the Boundary**:
- When light travels from an optically denser medium to an optically rarer medium, it encounters a boundary where it will change its speed and direction.

3. **Refraction and Snell's Law**:
- According to Snell's Law:
\[ \frac{N1}{N2} = \frac{\sin A}{\sin R} \]
where A is the angle of incidence and R is the angle of refraction.
- Since N1 > N2, it follows that the angle of refraction (R) will be greater than the angle of incidence (A). This means the light ray bends away from the normal.

4. **Changes in Velocity**:
- As light moves from a denser medium to a rarer medium, its speed increases. This is because the refractive index is inversely related to the speed of light in the medium.

5. **Changes in Wavelength**:
- The relationship between speed (V), frequency (f), and wavelength (λ) is given by:
\[ V = f \cdot \lambda \]
- Since the frequency (f) of light remains constant when it transitions between media, an increase in speed (V) must result in an increase in wavelength (λ).

6. **Conclusion**:
- Therefore, when light passes from an optically denser medium to an optically rarer medium:
- Its velocity increases.
- Its wavelength increases.
- Its frequency remains the same.
- Hence, the correct answer is **All of the above**.

### Final Answer:
The correct option is **All of the above**.