1. Physics 1230: Light and Color Ivan I. Smalyukh, Instructor Office: Gamow Tower, F-521 Email: ivan.smalyukh@colorado.edu Phone: 303-492-7277 Lectures: Tuesdays & Thursdays, 3:30 PM - 4:45 PM Office hours: Mondays & Fridays, 3:30 PM – 4:30 PM TA: Jhih-An Yang jhihan.yang@colorado.edu Class # 12

2. Announcements HW #3 Due today; Exam #1 - October 11; Overview of Exam #1 material today;

3. 3 1)A ray parallel to the axis is deflected through the focus on the other side 2)A ray through the center of the lens continues undeviated 3)A ray coming from the focus on one side goes out parallel to the axis on the other F’F’ F Ray might have to be extended 1 2 3 3 Thin convex lens: three easy rules for ray tracing foci } focal length

4. 4 1)A ray parallel to the axis is deflected as if it came from the focus 2)A ray through the center of the lens continues undeviated 3)A ray aimed at the focus on the other side comes out parallel F’F’ F Ray might have to be extended 1 2 3 For diverging lens focal length defined to be negative Thin concave (diverging) lens: three easy ray rules

5. Magnification formula S 0 = object height S i = image height Note the similar triangles. 5 Distances below the horizontal axis are defined as negative. Demo: big mama lens and bulb

6. Image distance equation F = focal length X O = object distance X I = image distance Usually, F is given. 6 Distant objects: Let X o be very large, say 1,000,000 meters. Then 1/X o = 0.000001, which is very small. You can ignore it. Then For distant objects, the image is at the focal point (ask a burnt ant) Demo: find focal length of lenses

7. What is lens power (or diopters)? Lens power: D = 1/F Units of D are 1/meters, also called diopters Eyeglass lenses are measured in diopters. Example: D = 2/m = what focal length? F = 1/D = 1/(2/m) = (1/2) m = 0.5 m

8. How thin lenses add F tot = final focal length F 1 = focal length lens 1 F 2 = focal length lens 2 Diverging lenses (concave) have negative focal lengths This is the same as adding powers: D tot = D 1 + D 2 8 Demo: put together some lenses

9. Compound Lenses Can have less aberration. A modern lens can have 16 elements and can “zoom”. 9 “stop” Reduces aberration Image plane

10. 10 Ch. 3 – Spherical mirrors and lenses 1.Virtual images (review) 2.Spherical mirrors 3.Spherical lenses 3 formulas 4.Aberrations of lenses We are here 10

11. Aberrations Field curvature Off-axis aberration Spherical aberration Distortion Chromatic aberration 11

12. Aberration: field curvature 12 Image does not lie in one plane

13. Off axis aberration Edges of images are less clear. 13 Demo with lens and bulb

14. Spherical aberration Rays at the edge focus closer to the mirror 14 Demo with lens, not mirror

15. Aberrations: Distortion 15 Demo with overhead and small lenses

16. Chromatic Aberration 16 Demo with lens and bulb

17. Web tutorials with Java Applets Useful web links on curved mirrors http://micro.magnet.fsu.edu/primer/java/mirrors/concavemirrors/index.html http://micro.magnet.fsu.edu/primer/java/mirrors/convexmirrors/index.html http://micro.magnet.fsu.edu/primer/java/mirrors/concave.html Useful web links on lenses http://micro.magnet.fsu.edu/primer/lightandcolor/lenseshome.html http://micro.magnet.fsu.edu/primer/java/lenses/simplethinlens/index.html http://micro.magnet.fsu.edu/primer/java/lenses/converginglenses/index.html http://micro.magnet.fsu.edu/primer/java/lenses/diverginglenses/index.html http://micro.magnet.fsu.edu/primer/java/components/perfectlens/index.html http://micro.magnet.fsu.edu/primer/java/mirrors/convex.html 17

18. Fresnel Lens Used in lighthouses 18 Fresnel stage light Lighthouse lens

19. 19 http://sandiartfullyyours.com/NewFiles/lighthouse3/images/Ponce%20Fresnell.jpg