Ch 7 Refraction Index 1 Incident Ray Angle

Ch. 7 Refraction Index (折射率) 1

Incident Ray Angle of reflection Reflected Ray Angle of incidence air glass Angle of Refraction Refracted Ray 2

Light travelling from air to glass normal incident ray angle of incidence air glass angle of refraction The light ray bends towards the normal. (偏向 法線) refracted ray 3

Law of refraction (折射定律) gle an normal of inc e nc ide incident ray reflected ray air glass 折射角 (angle of refraction) 折射線 = n (refractive index) (refracted ray) 4

Refractive index of some common materials Material Refractive index Air 1. 00 Water 1. 33 Alcohol (酒精) 1. 36 Perspex (有機玻璃) 1. 50 Glass 1. 50 – 1. 70 Diamond (鑽石) 2. 42 5

Refractive index (折射率) normal a air medium X X n. X – refractive index (折射率) of medium X 6

Class Practice 7. 1 air X 55 60 Refractive index of x = ? 7

Class Practice 7. 1 air X 55 60 n = sin i / sin r = sin 60 ° / sin (90 -55) ° = sin 60 ° / sin 35 ° = 1. 51 Answer is C 8

Class Practice 7. 2 air X air Y Z Which one has the largest refractive index ? 9

Class Practice 7. 2 air X air Y = n (refractive index) Z r↓ means n↑ ∵ rx > ry > rz ∴ nx < ny < nz answer is C 10

Class Practice 7. 3 11

Class Practice 7. 3 53 ° 32 ° 59 ° 40 ° 0. 7986 0. 5299 1. 51 0. 857 0. 643 1. 33 12

Class Practice 7. 4 (a) 50 air r water n = 1. 33 r =? 13

Class Practice 7. 4 (a) sin 50° / sin r = 1. 33 50 air r sin r = sin 50° / 1. 33 = 0. 576 water ∴ r = 35. 2° 14

Class Practice 7. 4 (b) 50 air n = 1. 33 r =? water r 15

Class Practice 7. 4 (a) i = 40 ° r 50 air water sin 40° / sin r = 1. 33 sin r = sin 40° / 1. 33 = 0. 483 ∴ r = 28. 9° 16

Homework: Assignment Book Chapter 6 & 7 (p. 10 -14) Deadline: 2010 -11 -15 (Mon) 17