When light is refracted into a medium

Options

A. its wavelength and frequency both increases
B. its wavelength increases but frequency remains unchanged
C. its wavelength decreases but frequency remains unchanged
D. its wavelength and frequency both decrease.

Answer

To solve the question regarding the behavior of light when it is refracted into a medium, we will analyze the relationship between speed, wavelength, and frequency of light.

### Step-by-Step Solution:

1. **Understanding Refraction**:
- Refraction occurs when light passes from one medium to another, causing a change in speed. This change in speed affects the wavelength of the light.

2. **Key Relationships**:
- The relationship between speed (v), wavelength (λ), and frequency (f) of light is given by the equation:
\[ v = f \cdot \lambda \]
- Here, \( v \) is the speed of light in a medium, \( f \) is the frequency, and \( λ \) is the wavelength.

3. **Frequency in Different Mediums**:
- The frequency of light is determined by the source and remains constant when light enters a different medium. Thus, \( f \) does not change during refraction.

4. **Effect of Medium on Speed**:
- When light travels from a rarer medium (like air) to a denser medium (like water or glass), its speed decreases. This is a fundamental property of light.

5. **Wavelength Changes**:
- Since the speed of light decreases in a denser medium and the frequency remains constant, we can deduce that the wavelength must also decrease. This is because:
\[ \lambda = \frac{v}{f} \]
- If \( v \) decreases and \( f \) remains constant, \( λ \) must also decrease.

6. **Analyzing the Options**:
- Now we can evaluate the options provided in the question:
- Option 1: Wavelength and frequency both increase. (Incorrect)
- Option 2: Wavelength increases, but frequency remains unchanged. (Incorrect)
- Option 3: Wavelength decreases, but frequency remains unchanged. (Correct)
- Option 4: Wavelength and frequency both decrease. (Incorrect)

7. **Conclusion**:
- The correct answer is **Option 3**: its wavelength decreases, but frequency remains unchanged.