1. Ch.7 Refraction Index (折射率)

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

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

4. Law of refraction (折射定律)
normal
reflected ray
angle of incidence
incident ray
glass
air
折射角
(angle of refraction)
折射線
(refracted ray)
= n (refractive index)

5. Refractive index of some common materials
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

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

7. Class Practice 7.1
55
60
air X
Refractive index of x = ?

8. n = sin i / sin r = sin 60 ° / sin (90-55) ° = sin 60 ° / sin 35 ° 55
Class Practice 7.1
55
60
air X
n = sin i / sin r
= sin 60 ° / sin (90-55) °
= sin 60 ° / sin 35 °
= 1.51
Answer is C

9. Which one has the largest refractive index ?
Class Practice 7.2
air X Y Z
Which one has the largest refractive index ?

10. ∵ rx > ry > rz ∴ nx < ny < nz answer is C
Class Practice 7.2
air X Y Z
= n (refractive index)
r↓ means n↑
∵ rx > ry > rz ∴ nx < ny < nz answer is C

11. Class Practice 7.3

12. Class Practice 7.3
53 °
32 °
0.7986
0.5299
59 °
40 °
0.857
0.643
1.51
1.33

13. Class Practice 7.4 (a) r
50
air
water
n = 1.33
r = ?

14. ∴ r = 35.2° r sin 50° / sin r = 1.33 sin r = sin 50° / 1.33 = 0.576
Class Practice 7.4 (a)
sin 50° / sin r = 1.33
sin r = sin 50° / 1.33
= 0.576
∴ r = 35.2° r
50
air
water

15. Class Practice 7.4 (b) r
50
air
water
n = 1.33
r = ?

16. ∴ r = 28.9° r i = 40 ° sin 40° / sin r = 1.33 sin r = sin 40° / 1.33
Class Practice 7.4 (a)
i = 40 °
sin 40° / sin r = 1.33
sin r = sin 40° / 1.33
= 0.483
∴ r = 28.9° r
50
air
water

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