Huygens Wave Theory and rectilinear propagation of light
As per 12th Physics textbook, it has been mentioned that according to Huygens wave theory of light, light does not travel in straight line.
But I have heard that it is wrong and rectilinear propagation of light is one of the merits of Huygens theory rather than demerit please clear my doubt
Asked by Mohammed Faiz Ansari
The wave nature of light becomes prominent only when the size of the aperture of the obstacle is comparable to the wavelength.
The light of wavelength λ coming through an aperture of width a can be considered to be in rectilinear motion up to a distance of
where ZF is called the Fresnel distance.
Thus, wavelength λ decreases, the limit for rectilinear propagation increases.This is the reason why we say, ray optics is valid when the limiting case wavelength λ tending to zero is applied.