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At a short distance from a point-like source, a wave propagates from it in a three-dimensional homogeneous and isotropic medium. The shape of the wavefront is ________.

Asked in GSEB Board March 2016 · Wavefronts and Huygens construction

Answer: (4) Spherical

Step-by-step solution

Given: a point-like source in a three-dimensional homogeneous and isotropic medium, observed a short distance away.

Idea: a wavefront joins the points the disturbance reaches at the same instant, so its shape is decided by how far the wave travels in each direction.

Homogeneous and isotropic together mean the speed v is the same everywhere and in every direction.

After a time t the disturbance has therefore reached every point at the same distance r = vt from the source.

In three dimensions that locus is the surface of a sphere centred on the source.

The wavefront is spherical.

Why the other options are wrong

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