Ultrasonic waves produced by a vibrating quartz crystal are

Options

A. only longitudinal
B. only transverse
C. both longitudinal and transverse
D. neither longitudinal nor transverse

Explanation

To solve the question about the type of ultrasonic waves produced by a vibrating quartz crystal, we can follow these steps:

### Step 1: Understand the Types of Waves
- **Longitudinal Waves**: In these waves, the particles of the medium move parallel to the direction of wave propagation. An example is sound waves in air.
- **Transverse Waves**: In these waves, the particles of the medium move perpendicular to the direction of wave propagation. An example is waves on a string.

### Step 2: Analyze Ultrasonic Waves
- Ultrasonic waves are sound waves that have a frequency above the audible range for humans (above 20 kHz). They are produced by vibrating sources, such as quartz crystals.

### Step 3: Determine the Nature of Ultrasonic Waves
- Ultrasonic waves, like all sound waves, are mechanical waves that require a medium to travel through. They are primarily longitudinal waves because the particles of the medium (like air or water) vibrate in the same direction as the wave travels.

### Step 4: Conclusion
- Based on the nature of ultrasonic waves, we can conclude that they are **only longitudinal waves**.

### Final Answer
- The correct option is: **Only longitudinal**.

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