2. Refraction and Snells Law SNC2D

3. Index of Refraction Light will travel more slowly in more dense materials. The ratio of the speed of light in a vacuum (or air) to the speed in the material is the index of refraction (or refractive index), n.

4. Analogy for Refraction Sand Pavement Air Glass Light bends into glass then returns along original path much as a rolling axle would when encountering a strip of mud. 3 x 10 8 m/s 2 x 10 8 m/s v s < v p

5. Index of Refraction: Example For water, the index of refraction is 1.33. The speed of light in water is therefore:

6. Index of Refraction: Example For water, the index of refraction is 1.33. The speed of light in water is therefore:

7. Index of Refraction: Example For water, the index of refraction is 1.33. The speed of light in water is therefore:

8. Boundaries So in 2D (with the boundary at an angle to the wave), the wave will bend as those parts that enter the more-dense material first slow down first. (The black lines show the crests or “wavefronts”).

9. Please Note! If the ray is perpendicular to the boundary, no bending will occur:

10. Snell’s Law The amount by which the wave is bent is given by Snell’s Law ( n i and n r are the refractive indices of the media).

11. Snell’s Law Note that a ray will always bend towards the normal when travelling into a more-dense medium

12. Snell’s Law Note that a ray will always bend towards the normal when travelling into a more-dense medium (and away from the normal when travelling into a less-dense medium).

13. Problem Solving with Snell’s Law When light passes from air into water at an angle of 45 o from the normal, what is the angle of refraction in the water?

14. Problem Solving with Snell’s Law When light passes from air into water at an angle of 45 o from the normal, what is the angle of refraction in the water?

15. Problem Solving with Snell’s Law When light passes from air into water at an angle of 45 o from the normal, what is the angle of refraction in the water?

16. Problem Solving with Snell’s Law When light passes from air into water at an angle of 45 o from the normal, what is the angle of refraction in the water?

17. Problem Solving with Snell’s Law When light passes from air into water at an angle of 45 o from the normal, what is the angle of refraction in the water?

18. Problem Solving with Snell’s Law When light passes from air into water at an angle of 45 o from the normal, what is the angle of refraction in the water?

19. Question-12 In traveling from air into water (n = 1.33), a ray of light makes an angle of incidence of 52 o. Calculate the angle of refraction. Click

20. Question-11 A ray of light enters water at an angle of incidence of 30 o. The angle of refraction is found to be 22 o. Calculate the index of refraction for water. Click

21. Question-13 In traveling from water into air, a ray of light makes an angle of refraction of 59 o. Calculate the angle of incidence. Click

22. Question-14 A ray of light emerges from water into air with an angle of incidence of 22 o. What is the angle of refraction? Click

23. Question-16 A light ray passes through two liquids, one floating on top of the other, in a beaker. The angle of refraction in the water is 25 o (see diagram). Determine the angle of incidence (A o ). Click

24. Links http://www.rpi.edu/dept/phys/ScIT/Infor mationTransfer/reflrefr/rr_sample/rrsampl e_15.html

25. Dispersion Note that since different wavelengths of white light refract slightly differently, refraction can split white light into its different wavelengths (i.e. colours) especially if refracted twice.

26. Dispersion Note that since different wavelengths of white light refract slightly differently, refraction can split white light into its different wavelengths (i.e. colours) especially if refracted twice.

27. Dispersion Note that since different wavelengths of white light refract slightly differently, refraction can split white light into its different wavelengths (i.e. colours) especially if refracted twice. This is called dispersion.