Question

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

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

• A.
• B.
• C.
• D.

Answer 1

The correct option is C

The amplitude of oscillation of the particles is maximum where the 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 given as,


Since pressure variation is given by , $\Delta P=-B\frac{dy}{dx}$
$\Rightarrow$ as the pressure variation is positive in the first half, slope of the displacement curve should be negative. This is only true for option $\left(c\right)$ .

So, below graph correctly represents the displacement of particles of the medium.