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Question
For light diverging from a point source ______.
- the wavefront is spherical.
- the intensity decreases in proportion to the distance squared.
- the wavefront is parabolic.
- the intensity at the wavefront does not depend on the distance.
Options
a and b
a and c
b and c
c and d
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Solution
a and b
Explanation:
| Type of wavefront | Intensity | Amplitude |
Spherical |
`I oo 1/r^2` | `A oo 1/r` |
Cylindrical |
`I oo 1/r` | `A oo 1/sqrt(r)` |
Plane |
`I oo 1/r^0` | `A oo r^0` |
Due to the point source light propagates in all directions symmetrically and hence, wavefront will be spherical as shown in the diagram.
As intensity of the source will be `I oo 1/r^2`
Where r is radius of the wavefront at any time.
Hence the intensity decreases in proportion to the distance squared.
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