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 of 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
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C
The wave intensity decreases as the inverse of square of the distance from the source for a spherical wave
c A plane wave does not have any radial dependence. Thus a plane wave travels with constant intensity. Intensity of a spherical wave decreases. It is because the power in the wave is carried and constant at all radius. Intensity is power distributed over the spherical surface area.
$I=\frac{P}{4 \pi r^{2}}$
For a cylindrical wave the power is same at all distance from the source. The power is distributed over the entire surface area.
$I=\frac{P}{2 \pi r l}$
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