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Question
Explain how Corpuscular theory predicts the speed of light in a medium, say, water, to be greater than the speed of light in vacuum. Is the prediction confirmed by experimental determination of the speed of light in water? If not, which alternative picture of light is consistent with experiment?
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Solution
No; Wave theoryNewton’s corpuscular theory of light states that when light corpusof two media moves from a rarer (air) to a denser (water) medium, the particles experience forces of attraction normal to the surface. Hence, the normal component of velocity increases while the component along the surface remains unchanged.Hence, c sin i=v sin ri = Angle of incidencer = Angle of reflectionc = Velocity of light in airv = Velocity of light in waterWe have the relation for relative refractive index of water with respect to air as μ=v/c
Thus, v/c=sin i/sin r=μHence, it can be inferred that v>c. This is not possible since this prediction is opposite to the experimental results of c>v.
The wave picture of light is consistent with the experimental results.
No; Wave theory
Newton’s corpuscular theory of light states that when light corpus
of two media moves from a rarer (air) to a denser (water) medium, the particles experience forces of attraction normal to the surface. Hence, the normal component of velocity increases while the component along the surface remains unchanged.
Hence, c sin i=v sin r
i = Angle of incidence
r = Angle of reflection
c = Velocity of light in air
v = Velocity of light in water
We have the relation for relative refractive index of water with respect to air as μ=v/c
Thus, v/c=sin i/sin r=μ
Hence, it can be inferred that v>c. This is not possible since this prediction is opposite to the experimental results of c>v.
The wave picture of light is consistent with the experimental results.
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