Question

A hospital uses an ultrasonic scanner to locate tumors in a tissue. What is the wavelength of ultrasonic sound wave in the tissue if scanner operates at $4.2\text{MHz}$ and velocity of sound in tissue is $1.7\text{km/s}$?

• A. $5.04\times {10}^{-4}\text{m}$
• B. $4.05\times {10}^{-4}\text{m}$
• C. $6.05\times {10}^{-4}\text{m}$
• D. $7.05\times {10}^{-4}\text{m}$

Answer 1

The correct option is B $4.05\times {10}^{-4}\text{m}$

We know that velocity of sound wave is given by,
$v=\lambda f$, where $\lambda$ is wavelength and $f$ is frequency.
$\Rightarrow \lambda =\frac{v}{f}$
$\Rightarrow \lambda =\frac{1.7\times {10}^3}{4.2\times {10}^6}=4.05\times {10}^{-4}\text{m}$