What is the shape of the wavefront from a distant star intercepted by Earth?
**Wavefront types** point source spherical, distant point source plane, after convex lens plane wave focuses to point because lens adds phase delay proportional to thickness, converging spherical wavefront, after concave mirror plane wave becomes spherical converging to focus, illustrating Huygens construction. At a large distance from a point source like a star, a small portion of the spherical wavefront appears plane. 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 interference, diffraction an
Ref: NCERT > Physics Book > Wave Optics > Wavefront and Huygens Principle