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 1.7 km/s. The wave length of sound in a tissue close to

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

Answer 1

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

Since, $v=\lambda f$
thus, $1.7\times 1000=\lambda \times 4.2\times {10}^6$
$\lambda =4\times {10}^{-4}$ m