# Physics II Lab w answers_Part_71 - Experiment 24 Speed of...

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153 Experiment 24 Speed of light in glass Apparatus Prism, spectrometer, monochromatic light source, spirit level. Objective To determine the speed of propagation of light waves in glass. Theory Light travels with the speed c = 2.998 × 10 8 m s -1 in vacuum. In a material medium its speed (v) is less. As a result, light waves undergo refraction at the interface of two media. In this experiment, we take the material of the medium in the form of a glass prism. A parallel stream of waves traveling from a medium 1 (here air) is incident on the interface of air and glass (of the prism), at the angle incidence θ 1. The angle of refraction is θ 2 . Snell’ s law connects the two by the relation, n 1 sin θ 1 = n 2 sin θ 2 … … … . .… … (1) where n 1 and n 2 are the refractive indices of the two media 1 and 2 respectively. Since the medium 1 here is air (n 1 1.000), the speed of light in the second medium is given by ν =c(sin θ 2 /sin θ 1 ) … … … … … … (2) We know that for a certain direction of incidence, the ray travels parallel to the base of the prism and the angular displacement of the final ray that emerges from the second interface of the prism has the lowest possible value. For this minimum angular deviation,

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## This note was uploaded on 11/26/2011 for the course PHY 2053 taught by Professor Lind during the Fall '09 term at FSU.

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Physics II Lab w answers_Part_71 - Experiment 24 Speed of...

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