Question

The variation in pressure in the medium due to propagation of sound is represented as

Which of the following graph correctly represent the displacement of particles of the medium?

• A.
• B.
• C.
• D.

Answer 1

The correct option is C

The amplitude of oscillation of the particle is maximum where pressure in the medium is zero and vice-versa.
Hence, pressure wave and displacement wave are out of phase by $\frac{\pi }{2}$.
For graph of pressure variation in the medium,

Since pressure variation, $\Delta P=-B\frac{dy}{dx}$
For pressure variation to be positive in the first half, slope of the displacement curve should be negative. This is true only for option $\left(c\right)$ .
Below graph of displacement of particle correctly represent the displacement of particles of the medium.