1. Quiz 4

2. Physics 7C Fall 2008 Lecture 5: Ray Optics Images Lens Types & Ray Tracing

3. Overview of next few weeks:

4. Terms in Optics Concepts: Object Image Real Virtual Upright Inverted Magnification Focus Reflection Refraction Ways to locate Image: Thin Lens Equation Image distance Object distance Sign of lens Ray Tracing Principal Rays Lens Types: Converging Diverging Convex Concave

5. What phenomenon most completely describes what you are seeing? a)Refraction b)Convergence c)Divergence d)Total Internal Reflection e)Snell’s Law

6. Light passes from water (n=1.3) into an unknown substance water ? At larger angles, will there be total internal reflection? a)Yes, past the critical angle b)No, not possible c)Not enough information

7. Review: Light at an Interface Activity 8.6.3 & FNT 1 Incoming Ray Plastic prism n = 1.5 Which Ray? (a) (b) (c) Air n = 1 (d)

8. Review: Light at an Interface Activity 8.6.3 & FNT 1 Incoming Ray Plastic prism n = 1.5 On leaving the prism, which way will the light bend? a) Upb) Downc) No bend

9. How will light emerge from the prism below? Incoming Rays a)Up b)Down c)Parallel d)Bent inward (converge) e)Bent outward (diverge)

10. How will light emerge from the prism below? Incoming Rays a)Up b)Down c)Parallel d)Bent inward (converge) e)Bent outward (diverge)

11. How will light emerge from the prism below? Incoming Rays a)Up b)Down c)Parallel d)Bent inward (converge) e)Bent outward (diverge)

12. Parallel rays are uncommon…how do lenses work on regular objects?

13. Diffuse reflection: rough surface reflects light in many directions. Still obeys law of reflection, just scatters at many different angles. Even flat surfaces like paper are not smooth to visible light. A flashlight beam shining on paper can be seen from most angles, not just the one complimentary to the incident. Paper

16. Every part of the tree reflects light, scattering it all directions. A ray diagram is used to simplify this picture.

17. What type of image does Ernie make? a)Real b)Virtual c)Upright d)Inverted e)Bigger f)Smaller

18. c Focal point, f Object plane Image plane oi

20. c Focal point, f Object plane o i Image plane

21. Where will the image be? How big will the image be?

22. You have a 2-lens system. You know only what the information shown below: ? f=-25cm Image created by first lens 25cm 100cm T/F: There is enough information to locate the image produced by the second lens.

23. You have a 2-lens system. You know only what the information shown below: ? f=-25cm Image created by first lens 25cm 100cm T/F: There is enough information to determine what type of lens the first lens must be.

24. You have a 2-lens system. You know only what the information shown below: ? f=-25cm Image created by first lens 25cm 100cm T/F: There is enough information to determine what type of lens the first lens must be. True: lens must be converging--make sure you know why! Extra question: what does the original object look like?

25. Suppose you replace the first lens with an identically shaped lens that has a higher index of refraction. ? f=-25cm Image created by first lens 25cm 100cm How will the blue arrow change: Bigger or smaller? Upright or inverted? Closer or further?

26. Suppose you replace the first lens with an identically shaped lens that has a higher index of refraction. ? f=-25cm Image created by first lens 25cm 100cm How will the blue arrow change: Bigger or smaller? Upright or inverted? Closer or further? Stuck? A higher index of refraction means light will bend more…so a bigger or smaller focal length?

27. Suppose you replace the first lens with an identically shaped lens that has a higher index of refraction. ? f=-25cm Image created by first lens 25cm 100cm How will the blue arrow change: Bigger or smaller? Upright or inverted? Closer or further? No change: same orientation

28. Quiz 5: Lenses You should bring a straight edge You may bring and index card with notes (3 inch x 5 inch)

29. Ray Model: really short version Hitting a boundary can lead to reflection or refraction, often both. We can calculate the angles for any outgoing ray- always with respect to normal Lenses are constructed carefully to bend light in particular ways to create images We can locate images with the thin lens equation or a ray tracing, and describe them in many ways