4 21 the index of refraction the velocity of light

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Unformatted text preview: tion, §26.7-8 • Polarized light, §24.6 1 • Brewster’s Angle, §26.4 2.1 The Index of Refraction The velocity of light inside a medium differs from the velocity of light in vacuum. The amount that the velocity changes also varies with the wavelength, λ of the light. We use the index of refraction, n(λ ) to relate the speed of light in the medium, v(λ ) to the speed of light in vacuum, c. Please note that n(λ ) means that the index is a function of the wavelength, not multiplied by the wavelength. n(λ ) ≡ c v(λ ) (1) In most media, n(λ ) does not change much with λ , so we often approximate n(λ ) by a value, n, which is an average value for visible light (λ ≈ 580 nm ≈ yellow). Typically, n = 1.3–2.5 for dense optical media such as plastic or glass. 2.2 Snell’s Law Snell’s Law is used to relate how light “bends” when it enters a material. Although it is called a “Law,” this is not strictly true because it can be derived from Maxwell’s Equations and the boundary conditions or from Fermat’s Principle. However, in this lab we will use the common title. Snell’s law states that if light passes from an incident material with index of refraction ni at some angle θi relative to the normal of the interface in...
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This document was uploaded on 02/15/2014.

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