Which of the following can not be polarised ?

Options

A. Radio waves
B. X-rays
C. Ultraviolet rays
D. Ultrasonic waves

Answer

To determine which of the following cannot be polarized, we need to understand the nature of different types of waves and their ability to undergo polarization.

### Step-by-Step Solution:

1. **Understanding Polarization**:
- Polarization refers to the orientation of the oscillations of a wave. For a wave to be polarized, it must have a transverse nature, meaning the oscillations occur perpendicular to the direction of wave propagation.

2. **Types of Waves**:
- **Electromagnetic Waves**: These include visible light, ultraviolet waves, and radio waves. They consist of oscillating electric and magnetic fields and can be polarized.
- **Sound Waves**: These are longitudinal waves where the oscillations occur in the direction of wave propagation. Sound waves cannot be polarized because their oscillations do not occur perpendicular to the direction of travel.

3. **Analyzing the Options**:
- **Option A**: Electromagnetic waves (can be polarized).
- **Option B**: Ultraviolet waves (can be polarized).
- **Option C**: Visible light (can be polarized).
- **Option D**: Ultrasonic waves (cannot be polarized).

4. **Conclusion**:
- Among the options provided, ultrasonic waves are the type of wave that cannot be polarized due to their longitudinal nature. Therefore, the correct answer is **Option D**.

### Final Answer:
**Ultrasonic waves cannot be polarized.**

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