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For light diverging from a point source |
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Answer» the wavefront is spherical.  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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