What is the shape of the wavefront emitted by a point source at a large distance?
**Wavefront** is locus of points in same phase, spherical from point source, plane at large distance because radius large, Huygens principle every point on wavefront acts as secondary source of wavelets, new wavefront envelope of secondary wavelets, allows prediction of new wavefront shape from known wavefront, explains reflection and refraction. At a large distance from a point source, the spherical wavefront appears plane over a small region. Using Δ = d sinθ, y = n λ D/d, a sinθ = n λ, I = I₀ cos²θ, n = c/v, sinC = 1/n, λ' = λ/n and A = 2a cos(φ/2), calculation gives Plane, illustrating int
Ref: NCERT > Physics Book > Wave Optics > Wavefront and Huygens Principle