Refraction and Lenses

1. Refraction and Lenses

2. Refraction • The change in direction or ‘bending’ of light.

3. Snell’s Law • Snell came up with a way to figure out how far light will ‘bend’ depending upon the medium the light traveled from and to. Link to interactive Snell’s Law Applet Willebrord van Roijen Snell1580-1626

4. Snell’s Actual Law n1 is the index of refraction for the incident medium. n2 is the index of refraction for the refracting medium. θ1 is the incident angle θ2 is the angle of refraction Link to Überdork’s ridiculous tribute to Snell’s law.

5. Example Problem 1 • A light beam in air hits a smooth lake at an angle of 30 degrees. At what angle is it refracted?

7. Index of Refraction and the Speed of Light n = index of refraction c = 3x108 m/s Vmaterial = Velocity of light in that material

8. Total Internal Reflection • Total internal reflection is a phenomenon that happens only when light passes from a more optically dense medium to a less dense optical medium. The incident ray’s angle is so ‘great’ that there is no refracted ray. Link to Total Internal Reflection Animation

9. Applications of Total Internal Reflection • Mirages • Fiber Optics • Diamonds Turn yourself into a diamond

10. Example Problem 5 • Find the critical angle for diamond.

11. Example Problem 6 • The critical angle for a special glass in air is 41 deg. What is the critical angle if the glass is immersed in water?

12. Dispersion of Light • The separation of light into it’s spectrum is called dispersion.

15. Lenses • Lens: Any transparent material with an index of refraction greater than that of air which re-directs lights path

16. Lens Equations

17. Convex Lens Anatomy

18. Convex Example Problem

20. Concave Lens Anatomy

21. Chromatic Aberration Chromatic Aberration – A defect where different colors are focused at different spots, especially at edges. Objects appear to be ringed in color.

22. Lens Applications

23. Nearsighted / Farsighted

24. Cameras