An Introduction to Refraction

1. An Introduction to Refraction SNC2D

2. 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.

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

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

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

6. Frequency and Wavelength Since the wave slows down but the frequency remains the same (the frequency of a wave is always the frequency of the source), the wavelength gets shorter.

7. 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”).

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

9. Snell’s Law The amount by which the wave is bent is given by Snell’s Law (ni and nr are the refractive indices of the media).

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

11. 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).

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

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

18. 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.

19. 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.

20. 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.

21. More Practice • p. 438 Practice Problems 1-3 (top set) • p. 441 Practice Problems 1-3 • p. 442 Practice Problems 1-3