Why does ultrasonic wave not exhibit polarisation?

Answer

### Step-by-Step Solution:

1. **Understanding Wave Types**:
- Waves can be classified into two main types: transverse waves and longitudinal waves.
- Transverse waves have oscillations that are perpendicular to the direction of wave propagation, while longitudinal waves have oscillations that are parallel to the direction of wave propagation.

2. **Examples of Waves**:
- An example of a transverse wave is light, which can be polarized.
- An example of a longitudinal wave is sound, which cannot be polarized.

3. **Polarization Phenomenon**:
- Polarization is a phenomenon that occurs with transverse waves, allowing them to oscillate in a particular direction.
- Longitudinal waves, on the other hand, do not have a direction of oscillation that can be restricted to a single plane.

4. **Ultrasonic Waves**:
- Ultrasonic waves are sound waves that have frequencies above the audible range for humans.
- Since ultrasonic waves are a type of sound wave, they are also longitudinal waves.

5. **Conclusion**:
- Because ultrasonic waves are longitudinal waves, they do not exhibit the phenomenon of polarization. This is due to the nature of longitudinal waves, which lack the ability to oscillate in a single plane.

### Final Answer:
Ultrasonic waves do not exhibit polarization because they are longitudinal waves, and longitudinal waves cannot be polarized.

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