Waves

Question : 7 of 27

Marks: +1, -0

A hospital uses an ultrasonic scanner to locate tumours in a tissue. What is the wavelength of sound in the tissue in which the speed of sound is 1.7

\text{km s}^{-1}

? The operating frequency of the scanner is 4.2 MHz.

Solution:

Here,

v = 1.7\,\mathrm{km\,s^{-1}}

= 1.7 \times 10^{3}\,\mathrm{m\,s^{-1}}

\upsilon = 4.2\,\mathrm{MHz} = 4.2 \times 10^{6}\,\mathrm{Hz}

Now,

\lambda = \frac{v}{\upsilon}

= \frac{1.7 \times 10^{3}}{4.2 \times 10^{6}} = 0.405 \times 10^{-3}\,\mathrm{m}

= 0.405 mm

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