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Aim: What happens to the speed of light in different mediums?. Do Now: What is the wavelength of yellow light?. v = f λ c = f λ 3 x 10 8 m/s = (5.20 x 10 14 Hz) λ λ = 5.8 x 10 -7 m. Index of Refraction ( n ).
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Aim: What happens to the speed of light in different mediums? Do Now: What is the wavelength of yellow light? v = f λ c = f λ 3 x 108 m/s = (5.20 x 1014 Hz) λ λ = 5.8 x 10-7 m
Index of Refraction (n) • Equal to ratio of speed of light (c) in vacuum to speed of light in material • Indicator of optical density
A ray of monochromatic light passes through a flint glass prism. What is the speed of the light ray in flint glass? n = c/v 1.66 = 3.00 x 108m/s v v = 3.00 x 108m/s 1.66 v = 1.81 x 108m/s
In a certain material, a beam of monochromatic light (f=5.09 x 1014 Hz) has a speed of 2.25 x 108 m/s. What is the material? n = c/v n = 3.00 x 108 m/s 2.25 x 108 m/s n = 1.33 WATER
Speed of light is constant… • Large n small v • Small n large v
Optical Density • Velocity of the wave in the new medium depends on optical density. • The more dense, the slower the velocity • Determines the direction and degree to which the ray will bend upon entering the new medium.
A beam of monochromatic light travels through flint glass, crown glass, lucite, and water. The speed of the light is slowest in • Flint glass • Crown glass • Lucite • Water
Relationship between n, v, and λ • We know: and So we can say: