1. 1 REFRACTION OF LIGHT

2. 2 Chapter 18 Objectives: 1) Define refraction of light including examples. 2) Know which direction a light ray bends as it travels between materials of different optical densities. 3) Define index of refraction and provide values for common materials such as air, water, and glass. 4) Apply Snell’s Law to a light ray traveling from one medium to another. 5) Explain total internal reflection. 6) Modify Snell’s Law to solve for critical angle. 7) Use total internal reflection to explain fiber optics, mirages, and rainbows.

3. 3 8) Define lens. 9) Describe how a convex lens uses refraction of light to form an image. 10) Be able to locate the image formed by a convex lens by using ray tracing diagrams and the lens equation. 11) Describe how a concave lens uses refraction of light to form an image. 12) Be able to locate the image formed by a concave lens by using ray tracing diagrams and the lens equation. 13) Describe the lens defects known as spherical aberration and chromatic aberration. 14) Know the main parts of the eye. 15) Differentiate between farsightedness and nearsightedness and how is each corrected.

4. 4 Chapter 18 Refraction and Lenses I) Refraction of Light A) ____________: The bending of a light wave as it travels from one medium to another, due to the changing of the speed of the wave.

5. 5 1) Light bends _______ the normal line as it slows down. The opposite is true when the wave speeds up.

6. 6 2) Snell’s Law of Refraction a) Snell’s Law: *where “n” is the index of refraction for the medium.

7. 7 b) _______________________: n, the ratio between the speed of light in space (a vacuum) and the speed of light in the medium.

8. 8 c) Common Indecies of Refraction: *more on page 486, Table 18-1.

9. 9 3) Sample Problem: A beam of light in air enters a piece of glass at an angle of 30.0 . At what angle will the light be refracted in the glass?

10. 10 B) Total Internal Reflection 1) __________________________: the complete reflection of light at the boundary of two transparent media; occurs when the angle of incidence is greater than the critical angle for the material.

11. 11 2) The critical angle from Snell’s Law:

12. 12 a) Fiber Optics: *used for:

13. 13 b) Mirages (atmospheric refraction):

14. 14 C) Dispersion of Light 1) ____________: The process of separating light into its component wavelengths (colors).

15. 15 a) In a raindrop: b) The Rainbow:

16. 16 II) Lenses A) Types of Lenses 1) ______: A transparent material that refracts light causing it to converge or diverge. 2) Convex (______________) Lens:

17. 17 a) Ray Tracing: a1) Object is “far away”:

18. 18 a2) Object is “close up”:

19. 19 3) Applying the LENS EQUATION: *See page 494, Table 18-2 for lens information. a) Sample Problem: A 3.0 cm tall object is placed 32.0 cm from a convex lens that has a focal length of 8.0 cm. (a) Where is the image? (b) How tall is the image?

20. 20

21. 21 4) Concave (____________) Lenses: a) Ray Tracing: a1) Object beyond “F”:

22. 22 a2) Object inside “F”:

23. 23 III) Lens Defects: A) Spherical Aberration: 1) Corrected by limiting the amount of lens exposed to the light (using an ______________).

24. 24 B) Chromatic Aberration: 1) Corrected using a two lens system:

25. 25 IV) The Eye: *The image formed on the retina is always:

26. 26 * _______________:muscles in the eye change the thickness of the eye’s lens.

27. 27 2) Myopia (____________________): Able to see things better when they are close up.

28. 28 3) Hyperopia (___________________): Able to see things better when they are far away.