# Is the Huygens' principle consistent for intersecting wavefronts?

When refraction takes place at the interface of two media, wavefronts can be extended to intersect as below:

At point of intersection, light requires no time to travel between the wavefronts. However, between other point on the wavefront, time is rquired by the light to travel.

This clearly contradicts Huygens' principle which states that the time taken by light to travel between two wavefronts is irrespective of path taken by it.

What am I missing?

• The Huygens principle states that every point on a wavefront is itself the source of spherical wavelets, and the secondary wavelets emanating from different points mutually interfere. Throw a ball in a poll. The generated wave reach to wall of pool at different time. This because of the points on wall meet wavefront at different times. When light passes from one medium to another, it refracts at the interface. Commented Mar 1 at 7:34
• According to Huygens’s principle, each point on the incident wavefront becomes a source of secondary wavelets. These secondary wavelets propagate in the new medium, and their envelope forms the refracted wavefront. So that, part of wave front still doesn't reach to intersection of two media and part of it refracted. Commented Mar 1 at 7:58
• @Sancol. Ah, I see, so it can be said that these point on the extension of the wavefronts do not lie on the locus of wavefront? Commented Mar 1 at 9:34