Waves - Result Question 25
25. 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 wavelength of sound in tissue is close to
(a) $4 \times 10^{-4} m$
(b) $8 \times 10^{-4} m$
(c) $4 \times 10^{-3} m$
(d) $8 \times 10^{-3} m$
[1995]
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Answer:
Correct Answer: 25. (a)
Solution:
- (a) Frequency $(n)=4.2 MHz=4.2 \times 10^{6} Hz$ and speed of sound $(v)=1.7 km / s=1.7 \times 10^{3} m /$ s. Wave length of sound in tissue,
$\lambda=\frac{v}{n}=\frac{1.7 \times 10^{3}}{4.2 \times 10^{6}}=4 \times 10^{-4} m$
