As a wave propagates
(i) the wave intensity remains constant for a plane wave
the wave intensity decreases as the inverse of the distance from the source for a spherical wave
(iii) the wave intensity decreases as the inverse square of the distance from the source for a spherical wave
(iv) total intensity of the spherical wave over the spherical surface centred at the source remains constant at all times

Options

A. (i), (ii)
B. (i), (iii)
C. (i), (iii), (iv)
D. (i), (iii), (iv)

Answer

D