Page 29 - GALIET PHYSICS BLOSSOMS II+

The principle further states that the surface A'B', tangent to all the wavelets, constitutes the new wave front. It is apparent from Figure 12-4 that spherical wave fronts are propagated from spherical wavelets and planar wave fronts from planar wavelets.24
Based on these observations, Huyghens went on to posit that light is not a particle at all, but a wave in an immaterial, ultra stiff medium – the aether, which had to be very stiff to avoid compression under large pressures, and which had the power to transmit waves at really high velocity. Though light is a vibration of the aether, and the aether permeates everything including solid and liquid matter and its particles interact very strongly, it does not act or interact with matter directly. One feels, instead, the waves’ effects. Hence, motion of matter and only matter generates light waves, and light waves act upon matter. This aether has an immense number of very tiny and extremely hard spherical particles in close contact with each other. This medium could propagate light waves simultaneously in all directions with high velocity and in such a way that light waves travelling in different directions, at one and the same time, would not hinder each other’s progress. Surely, the light waves travel very fast, but not infinitely fast, spreading out uniformly in all directions just as a wave propagates. Moreover, Huyghens recognized that light does not interact with itself, it is not itself material, and that every luminous thing necessarily contains an immense number of centres emitting light. From each of these centres, thousands of waves may emerge in the smallest lapse of time.25
Reflection, Refraction and Simultaneous Reflection and Refraction
From this simple principle, Huyghens went on to explain purely on geometric constructions how reflection, refraction and simultaneous reflection and refraction followed naturally from his theory of wave propagation through the aether. He assumed that the waves travelled at different speeds in different media, explaining reflection and refraction easily.
To Huyghens, the elements of the boundary area separating the two media become the sources where partial waves travel out into the two media. When the partial waves are returned from the boundary into the upper, first medium, they build up the reflected wave, while those travelling into the lower, second medium, build up the refracted wave, explaining in this way, too, simultaneous reflection and refraction.26 Please see the drawings in
24 http://boomeria.org/physicstextbook/ch12.html
25 Stamp, Phillip. Optics and the Nature ofLight. 2012 Class Notes. 6-8. See also Raman, C.V. Optics. Christiaan Huyghens and the Wave Theory ofLight. 359.
26 Raman, C.V. Optics. Christiaan Huyghens and the Wave Theory ofLight. 360. http://dspace.rri.res.in/bitstream/2289/1997/1/1959%20Proc%20Indian%20Acad%20Sci%20A%20V49%20p185-192.pdf
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