Question

A hospital uses an ultrasonic scanner to locate tumours in a tissue. The operating frequency of the scanner is 4.2 MHz. The speed of sound in a tissue is $1.7Km/s$. The wavelength of the sound in the tissue is close to

• A. $4\times {10}^{–4}m$
• B. $8\times {10}^{–4}m$
• C. $4\times {10}^{–3}m$
• D. $8\times {10}^{–4}m$

Answer 1

The correct option is A $4\times {10}^{–4}m$

We know that the velocity of a sound wave is given as

$V=frequency\left(\nu \right)\times wavelength\left(\lambda \right)$

Therefore, the wavelength

$\lambda =\frac{V}{\nu }=\frac{1.7\times {10}^{3}m/s}{4.2\times {10}^{6}Hz}$
$\lambda =0.4047\times {10}^{-3}$
$\lambda =4\times {10}^{-4}m$