Light - 05 - Refraction - Intro | High School

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High School
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High School Physics
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2024
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7 Refraction Please Write this 7.0 Refraction:  The change in direction of a light ray due to a change in its speed  Occurs when light ray transfers from one medium to another medium with a different refractive index Reflected Ray Air Glass Incident Ray r  i Refracted Ray R  How much refraction occurs is dependent on the refractive index & angle of incidence Please Write this ☺  Light bends toward the normal when it enters a medium of greater refractive index Air Water Please Write this ☺  Light bends away from the normal when it enters a medium of lesser refractive index Air Water If angle of incidence = 0, no refraction  Ex. ◼ Stick bends in water ◼ Sun looks oval when setting “Shimmering” heat or “shimmering” roads Why objects under water appear at different depths ◼ ◼ 7.1 Refractive Index: Please Write this ☺  The refractive index (n) of a medium is a measure of how much the speed of light is reduced inside the medium c n= v c = 3.00 x 108 m/s (speed of light in a vacuum) v = speed of light in a given medium Ex #1 Please Write this ☺ In water the speed of light is 2.25 x 108m/s. What is the refractive index of water? c n= v 3.00 •10 n= 8 2.25 •10 8 n = 1.33 This means that light travels 1.33 times faster in air than in water. Medium Air Refractive Index 1.0003 Water 1.33 Plexiglas 1.51 Glass (crown) 1.52 Diamond 2.42 The higher the refractive index, the slower light travels Ex #2 The index of refraction of diamond is 2.42. What is the speed of light in diamond? c n= v 3.00 •10 2.42 = v 8 v = 1.24 • 10 m / s 8 7.2 Snell’s Law: Please Write this ☺  Re-discovered in early 1600s, was found that when the incident medium is air:  Generally: sin i n= sin  R n1 sin1 = n2 sin 2 Index of refraction for incident medium Angle of incidence Index of refraction for refracting medium Angle of refraction Ex #3 Please Write this ☺ Light travels from air into water. If the angle of incidence is 30o, and the refractive index of water is 1.33, what is the angle of refraction? n1 sin1 = n2 sin 2 0 (1) sin 30 = (1.33) sin 2  2 = 22 0 Ex #4  2 = 15 0 Light passes through a block of glass (n=1.54). The angle of incidence is 15o. Then the refracted ray leaves the glass into the air. What is the angle of refraction upon exiting the glass? 15o   R n1 sin1 = n2 sin 2 0 (1) sin15 = (1.54) sin  2 0  2 = 9.68 n1 sin1 = n2 sin 2 0 (1.54) sin 9.68 = (1) sin  2 Ex #5 Please Write this ☺ A fisherman is looking at a fish. Given that the index of refraction of water is 1.33, at what angle do the light rays enter the water before reaching the eyes of the fish? n sin = n sin 0 1 1 2 ? = 35 2 o (1) sin  = (1.33) sin 38 0 i i = 55  =? AIR WATER 52 38o HW: pg 81 #1, 2, 4 & 7 pg 83 #1a, 2 Quantum: