Question

A hospital uses an ultrasonic scanner to locate tumours in a tissue. The operating frequency of the scanner is 3.2 MHz. The speed of sound in a tissue is 1.6 km s–1. The wavelength of sound in the tissue is

• A. 0.25 mm
• B. 0.5 mm
• C. 0.75 mm
• D. 1 mm

Answer 1

Answer: (B)

0.5 mm

Answer 2

Here,

$\upsilon = 3.2MHz = 3.2 \times 10^{6}Hz = 3.2 \times 10^{6}s^{- 1}$

$v = 1.6kms^{- 1} = 1.6 \times 10^{3}ms^{- 1}$

Wavelength, $\lambda = \frac{v}{\upsilon} = \frac{1.6 \times 10^{3}ms^{- 1}}{3.2 \times 10^{6}s^{- 1}}$

$0.5 \times 10^{- 3}m = 0.5mm$