Question

The amplitude of a wave at a distance r form a point source is a, the amplitude at a distance 2r will be

Answer 1

Answer:

A/2

Explanation:

A point source produces a spherical wave assuming medium is isotropic.

Wave energy will be conserved as it propagates through air. In a spherical pressure wave of radius r, the energy of wavefront is spread out over the spherical surface area = 4πr².

Therefore, the energy per unit area of an expanding spherical wave decreases as 1/r² (Spherical Spreading Loss)

The intensity related to wave varies as = (1/r²).

Intensity is proportional to square of amplitude (A²).

As per inverse square law for energy translates to 1/r decay law for amplitude. Thus, A varies as (1/r).

When r is doubled, A will become A/2.