If the wave changes its medium then which of the following physical quantity changes?

Options

A. wavelength of wave
B. frequency of wave
C. speed of wave
D. both (1) and (3)

Answer

To determine which physical quantity changes when a wave transitions from one medium to another, we need to analyze the behavior of waves in different media.

### Step-by-Step Solution:

1. **Understanding Wave Properties**:
- A wave is characterized by its speed (v), frequency (f), and wavelength (λ). The relationship between these quantities is given by the equation:
\[ v = f \cdot \lambda \]

2. **Effect of Medium Change on Frequency**:
- When a wave travels from one medium to another, the frequency (f) of the wave remains constant. This is because the frequency is determined by the source of the wave and does not depend on the medium through which it travels.

3. **Effect of Medium Change on Speed**:
- The speed (v) of the wave changes when it enters a different medium. For example, sound travels faster in water than in air. The speed of light also changes when it moves from air into a denser medium like glass.

4. **Effect of Medium Change on Wavelength**:
- Since the frequency remains constant and the speed changes, the wavelength (λ) must also change to satisfy the wave equation. If the speed increases, the wavelength increases; if the speed decreases, the wavelength decreases.

5. **Conclusion**:
- Therefore, when a wave changes its medium, the quantities that change are the speed (v) and the wavelength (λ), while the frequency (f) remains unchanged.

### Final Answer:
The physical quantities that change when a wave changes its medium are **wavelength and speed of the wave**.

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