Question

As a wave propagates,
A. The wave intensity remains constant for a plane wave
B. The wave intensity decreases as the inverse of the distance from the source for a spherical wave
C. The wave intensity decreases as the inverse square of the distance from the source for a spherical wave
D. Total intensity of the spherical wave over the spherical surface centred at the source remains constant at all time

Answer 1

Correct Answer - A::C::D
For a plane wave intensity (energy crossing per unit area per unit time) is constant at all points

But for a spherical wave, intensity at a distance r from a point source of power P (energy transmitted per unit time) is given by :

`I=(P)/(4pir^(2))orIprop (1)/(r^(2))`