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 solve the question, "If the wave changes its medium then which of the following physical quantity changes?", we can analyze the properties of waves as they transition between different media.

### Step-by-Step Solution:

1. **Understanding Wave Properties**:
- A wave has three main properties: frequency (f), wavelength (λ), and speed (v).
- The frequency of a wave is determined by the source that generates it, while the wavelength and speed can change depending on the medium through which the wave travels.

2. **Frequency**:
- When a wave travels from one medium to another, the frequency remains constant. This is because the frequency is solely dependent on the source of the wave.
- Therefore, if the frequency before the transition is f, it remains f after the transition.

3. **Wavelength**:
- The wavelength of a wave is influenced by the medium. When a wave enters a different medium, its speed changes, which in turn affects its wavelength.
- For example, if the wavelength in medium 1 is λ₁ and in medium 2 is λ₂, we can say that λ changes when the medium changes.

4. **Speed**:
- The speed of a wave is also dependent on the medium. When a wave moves from one medium to another, its speed changes.
- If the speed in medium 1 is v₁ and in medium 2 is v₂, then v will change when the medium changes.

5. **Conclusion**:
- From the analysis, we conclude that when a wave changes its medium:
- The frequency remains the same (does not change).
- The wavelength changes.
- The speed changes.
- Therefore, the correct answer is that both the wavelength and speed of the wave change when the wave transitions between media.

### Final Answer:
The physical quantities that change are the wavelength of the wave and the speed of the wave. Thus, the answer is option 4: both 1 (wavelength) and 3 (speed).

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