Question

Read the following statements carefully.
(A) The SI unit of wave velocity is metre per second
(B) Frequency of a wave does not change with change in medium
(C) The speed of sound in a medium depends on temperature of the medium
(D) The speed of sound increases with increase in density of air
Choose the correct statements:

• A. Only (A) and (B)
• B. Only (B) and (C)
• C. Only (C) and (D)
• D. (A), (B) and (C)

Answer 1

The correct option is D (A), (B) and (C)

Wave velocity, $v=\lambda f$
Here, $\lambda =wavelength$ and f = frequency
The SI unit of wave velocity is $m{s}^{–1}.$
The speed and wavelength of a wave change when it goes from one medium to other, while its frequency remains same. The speed of sound is directly proportional to the square root of temperature of the medium i.e., $v\propto \sqrt{T}$
The speed of sound increases with the increase in temperature. The molecules of the medium at higher temperatures having more energy, can vibrate faster and allow sound wave to travel more quickly.
The speed of sound is inversely proportional to the square root of the density of air i.e., $v\propto \frac{1}{\sqrt{\rho }}$
Thus, the speed of sound decreases with the increase in density of air.
Hence, the correct answer is option (d).