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 km s–1 ? The operating frequency of the scanner is 4.2 MHz
Solution and Explanation
Speed of sound in the tissue, v = 1.7 km/s = 1.7 × 103 m/s
Operating frequency of the scanner, ν = 4.2 MHz = 4.2× 106 Hz
The wavelength of sound in the tissue is given as:
\(λ=\frac{v}{v}\)
\(=\frac{1.7×10^3}{4.2×10^6}=4.1×10^{-4}\,m\)
Top CBSE Class XI Physics Questions
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Top CBSE Class XI Transverse and longitudinal waves Questions
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- A steel wire has a length of 12.0 m and a mass of 2.10 kg. What should be the tension in the wire so that speed of a transverse wave on the wire equals the speed of sound in dry air at 20 °C = 343 m s–1 .
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A transverse harmonic wave on a string is described by
y(x, t) = 3.0 sin (36 t + 0.018 x + \(\frac{π}{4}\))
where x and y are in cm and t in s. The positive direction of x is from left to right.
(a) Is this a travelling wave or a stationary wave ? If it is travelling, what are the speed and direction of its propagation ?
(b) What are its amplitude and frequency ?
(c) What is the initial phase at the origin ?
For the travelling harmonic wave
y(x, t) = 2.0 cos 2π (10t – 0.0080 x + 0.35)
where x and y are in cm and t in s. Calculate the phase difference between oscillatory motion of two points separated by a distance of
(a) 4 m,
(b) 0.5 m,
(c) \(\frac{λ}{2}\),
(d) \(\frac{3λ}{4}\)
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- An oxygen cylinder of volume 30 litre has an initial gauge pressure of 15 atm and a temperature of 27 °C. After some oxygen is withdrawn from the cylinder, the gauge pressure drops to 11 atm and its temperature drops to 17 °C. Estimate the mass of oxygen taken out of the cylinder (R = 8.31 J mol–1 K–1, molecular mass of O2 = 32 u).
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