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For light diverging from a point source...

For light diverging from a point source

A

the wavefront is spherical.

B

the intensity decreases in proportion to the distance squared.

C

the wavefront is parabolic.

D

the intensity at the wavefront does not depend on the distance.

Text Solution

Verified by Experts

The correct Answer is:
A, B

Wavefront Wavefronts emitted from point like source and then propagating in three dimensional, homogeneous isotropic medium are found to be spherical in shape as shown in the figure (because at a given instant of time, phases of oscillations of light vectors are same at all the points on such spherical surface and so according to definition such a surface becomes sphercial wavefront). Thus option (A) is correct.
Here since power of a given source is constant, we have
P = IA = constant
`:.Iprop(1)/(A)`
`:.Iprop(1)/(r^(2))`
( `:.` Area of spherical surface is `A=4pir^(2)` )
Option (B) is also correct.
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