Page 32 - GALIET PHYSICS BLOSSOMS II+

• He also needed to explain why light moves slower in dense solid or liquid matter than in air, and why is it that light in air moves faster than in a vacuum?
Though Huyghens tries to explain how aether particles recoil slowly in a dense medium, his explanation is odd since it implies that aether flows around the medium’s solid atoms. This does not reconcile with the idea that the dense medium does not meet any resistance to motion through the aether, or vice versa.
Other weaknesses concerned Huyghens’ inadequate explanations of opacity, diffraction, and his arguments concerning the relative densities of water and mercury. Newton felt that the wave theory could not explain the existence of opaque things given that any wave incident on the surface of some opaque object would excite surface waves like those of water, and these would need to propagate into the object. Newton also felt it could not explain diffraction based on sound waves’ diffraction, because this had not been observed. Neither could it define the phenomenon of Newton’s Rings, though later it did support wave theory!33
(iii) Explain one way in which you think one can distinguish between the predictions of Newton, and those of Huyghens, for the properties of light.
Newton (and Descartes) had predicted that light travels faster in a dense medium, while Huyghens predicted that light travels slower in a dense medium.
Unlike Newton (and Descartes), Huyghens oddly argued that aether particles recoiled slower in a dense medium. To him, aether particles flowed around the medium’s solid atoms, which is rather odd given that there is no resistance to motion in dense mediums through the aether and vice versa.34
Indeed, Newton’s theory conflicted with Huyghens’ theory and with Fermat’s observation concerning how light propagates. Fermat believed that if light passed slowly through a dense medium, then it would take the least time for the light to pass between two points. In this way, Huyghens’ theory corroborated Fermat’s observation.35
33 Stamp, Phillip. Optics and the Nature of Light. 2012 Class Notes. 26. 34 Stamp, Phillip. Optics and the Nature of Light. 2012 Class Notes. 12. 35 Stamp, Phillip. Optics and the Nature of Light. 2012 Class Notes. 17.
•32•