If a wave is going from one medium to another, then

Options

A. its frequency change
B. wavelength does not change
C. velocity does not change
D. amplitude may change

Explanation

To solve the question about what happens when a wave goes from one medium to another, we will analyze the properties of the wave: frequency, wavelength, velocity, and amplitude.

### Step-by-Step Solution:

1. **Understanding Frequency**:
- When a wave travels from one medium to another, the frequency of the wave remains constant. This is because frequency is determined by the source of the wave and does not depend on the medium through which the wave is traveling.
- **Conclusion**: Frequency remains the same.

2. **Understanding Velocity**:
- The velocity of the wave is dependent on the properties of the medium, such as tension and mass per unit length (μ). When the wave enters a different medium, these properties may change, leading to a change in the wave's velocity.
- **Conclusion**: Velocity may change.

3. **Understanding Wavelength**:
- The relationship between velocity (v), frequency (f), and wavelength (λ) is given by the equation:
\[ v = f \cdot \lambda \]
- Since the frequency remains constant and the velocity may change when the wave enters a new medium, the wavelength must also change to satisfy this equation.
- **Conclusion**: Wavelength changes if velocity changes.

4. **Understanding Amplitude**:
- The amplitude of the wave can change when it enters a new medium. This change is influenced by the energy loss due to reflection and absorption in the new medium. If there is energy loss, the amplitude may decrease; if there is no loss, it may remain the same.
- **Conclusion**: Amplitude may change.

### Final Summary:
- When a wave travels from one medium to another:
- Frequency remains the same.
- Velocity may change.
- Wavelength changes if velocity changes.
- Amplitude may change depending on energy loss.