Question

What is the near field length \(N\) that can be calculated from the relation (if \(D\) is the diameter of the transducer and \(\lambda\) is the wavelength of sound in the material)?

• A. \(D^2 / 2\lambda\)
• B. \(D^2 / 4\lambda\)
• C. \(2D^2 / \lambda\)
• D. \(4D^2 / \lambda\)

Hint:

- Near field length (N) determines the focusing and directivity of ultrasonic waves.

Answer 1

The Correct Option is A

Step 1: Understanding near field length in acoustics. 
- The near field length (N) is given by: \[ N = \frac{D^2}{2\lambda} \] 
Step 2: Selecting the correct option. 
Since the correct formula is \(D^2 / 2\lambda\), the correct answer is (A).