1. 10-Aug-15 Physics 1 (Garcia) SJSU Chapter 28 Reflection & Refraction

2. 10-Aug-15 Physics 1 (Garcia) SJSU Specular and Diffuse Reflection Reflection from most surfaces is diffuse, with incoming light scattered in all directions. Reflection from mirror surfaces is specular, with light reflecting in one direction. Mirror Diffuse reflection Specular reflection

3. 10-Aug-15 Physics 1 (Garcia) SJSU Check Yourself What objects in this room radiate light? Is the projector screen radiating visible light? Is the screen diffuse or specular reflector?

4. 10-Aug-15 Physics 1 (Garcia) SJSU Diffuse Surface is Not a Mirror Light rays diffusely scatter in every direction from every spot on the surface. See a light ray from the top of your head reflected from this spot. Also see light ray from the tip of your nose reflected from this spot. Look at this spot on a diffuse surface

5. 10-Aug-15 Physics 1 (Garcia) SJSU Pinhole Camera Small pinhole allows only small amount of light in, blocking overlapping diffuse rays and forming image inside the camera.

6. 10-Aug-15 Physics 1 (Garcia) SJSU Camera Obscura The camera obscura (room darkened) dates to ancient times; it was first detailed in the writings of Leonardo da Vinci. A room is completely sealed from light except for a coin-sized hole in one wall. An image of the outside world appears projected, upside down and reversed right-to-left, onto a wall opposite the opening. A portable camera obscura, equipped with a mirror at a 45-degree angle, reflects the image upward and focuses it on a viewing screen. Artist’s secret drawing weapon? Diffuse light

7. 10-Aug-15 Physics 1 (Garcia) SJSU Drawing Skill or Optical Aids? Portrait of Giovanni Arnolfini and his Wife (1434) by Hubert and Jan van EYCK Was the chandelier drawn by van Eyck using optical aids, such as a camera obscura?

8. 10-Aug-15 Physics 1 (Garcia) SJSU Transparent, Reflecting Surfaces Water and glass are transparent but reflect some of the light striking their surface. Can see inside the cab through the right window. Strong reflection of the sun on the left window. Can see some of the riverbed through the water surface.

9. 10-Aug-15 Physics 1 (Garcia) SJSU One Way Mirror One way mirror is just clear glass window. Bright Room Dark Room Discussion Room (Bright) Observation Room (Dark) GLASS Reflected light from bright room masks transmitted light from the darkened observation room

10. 10-Aug-15 Physics 1 (Garcia) SJSU Law of Reflection Angle of incidence equals angle of reflection SPECULAR REFLECTION

11. 10-Aug-15 Physics 1 (Garcia) SJSU Demo: Blackboard Optics Special blackboard has mounted light source and mirrors. Light Source Mirror Demonstrates the Law of Reflection Incident Reflected

12. 10-Aug-15 Physics 1 (Garcia) SJSU Ray Tracing Light ray from point A is reflected at point B and arrives at point B. Notice the relationship between point B (where the ray is reflected to) and point B’ (where the ray would go if the mirror wasn’t there).

13. 10-Aug-15 Physics 1 (Garcia) SJSU Demo: Who Do You See? Which person in the front row sees the guy with the hat (person F) in the mirror? F ABC DEG MIRROR

14. 10-Aug-15 Physics 1 (Garcia) SJSU Mirror Image Reflection To observer at point B, the light from point A seems to come from point A’, within mirror.

15. 10-Aug-15 Physics 1 (Garcia) SJSU Plane (Flat) Mirror Tracing light rays from original, to mirror, to eye allows us to construct image. Original Image Mirror HAIR NOSE CHIN

16. 10-Aug-15 Physics 1 (Garcia) SJSU Demo: Pocket Mirror See full image of your head in a plane mirror that’s half the size of your head. Original Image Mirror

17. 10-Aug-15 Physics 1 (Garcia) SJSU Image in the Mirror Utamaro, Woman Powdering Her Neck Velazquez, Venus at her Mirror Helmut Newton, Bergstrom over Paris Image is seen an equal distance from original within a plane mirror. Incorrect Correct

18. 10-Aug-15 Physics 1 (Garcia) SJSU Non-Flat Mirrors Image in a curved mirror is distorted from original. Determine image location and size by ray tracing

19. 10-Aug-15 Physics 1 (Garcia) SJSU Demo: Convex Mirrors Mirrored surface on a sphere or similar rounded shape. Image is smaller & closer. MC Escher Hand with Reflecting Sphere

20. 10-Aug-15 Physics 1 (Garcia) SJSU Demo: Blackboard Convex Mirror Can use optics blackboard to trace diverging rays from convex mirror. Law of reflection still holds but mirror surface is curved.

21. 10-Aug-15 Physics 1 (Garcia) SJSU Ray Tracing for Convex Mirror Image in convex mirror is smaller & closer. Original Image Mirror

22. 10-Aug-15 Physics 1 (Garcia) SJSU Image in the Mirror #2 Portrait of Giovanni Arnolfini and his Wife (1434) by Hubert and Jan van EYCK

23. 10-Aug-15 Physics 1 (Garcia) SJSU Demo: Concave Mirrors Mirror is on the inner curved surface of sphere or similar rounded shape. Image size and location depends on object’s distance from the mirror. Telescope

24. 10-Aug-15 Physics 1 (Garcia) SJSU Demo: Blackboard Concave Mirror Use optics blackboard to trace convergence of rays from concave mirror. Notice that rays focus to a point (the focal point) then diverge, as with convex mirror. Focal Point

25. 10-Aug-15 Physics 1 (Garcia) SJSU Ray Tracing for Concave Mirror Image in concave mirror is larger when original is close to the mirror. Original Image Mirror

26. 10-Aug-15 Physics 1 (Garcia) SJSU Image Ray Tracing for Concave Mirror Image in a concave mirror is inverted if the original is far away from the mirror. Image is formed in front of the mirror, not within it. Original Mirror

27. 10-Aug-15 Physics 1 (Garcia) SJSU Demo: Forming a Real Image Locate the image formed in front of a concave mirror using a strong light source and a screen. Candle Image Screen

28. 10-Aug-15 Physics 1 (Garcia) SJSU Reflecting Telescopes Large, modern telescopes form images using concave mirrors. Hubble’s mirror Magellan Telescope

29. 10-Aug-15 Physics 1 (Garcia) SJSU Refraction Light rays bend (refract) passing from water to air, making objects appear to be shallower and closer to the observer. Image Actual Image Actual Observer sees image

30. 10-Aug-15 Physics 1 (Garcia) SJSU Law of Refraction Light passing from one material to another is refracted by a fractional angle that depends on the optical density of each material. Angle is smaller in the denser material.

31. 10-Aug-15 Physics 1 (Garcia) SJSU Demo: Refraction thru Block Light is refracted entering the block and refracted back on leaving the block.

32. 10-Aug-15 Physics 1 (Garcia) SJSU Check Yourself Which path does light ray take after entering the wedge? Which path does it take after leaving the wedge? A B C D E F WEDGE

33. 10-Aug-15 Physics 1 (Garcia) SJSU Lenses Curvature of a lens surface produces a continuous, variable angular refraction. Concave lens shrinks its image Convex lens magnifies its image

34. 10-Aug-15 Physics 1 (Garcia) SJSU Demo: Concave Lenses Curved surface of a concave lens causes light rays to diverge, shrinking images.

35. 10-Aug-15 Physics 1 (Garcia) SJSU Demo: Convex Lenses Curved surface of a convex lens causes light rays to converge, magnifying images

36. 10-Aug-15 Physics 1 (Garcia) SJSU Demo: Real Image of Convex Lens Image formed by convex lens can be observed on a screen.

37. 10-Aug-15 Physics 1 (Garcia) SJSU Total Internal Reflection When refraction angle exceeds 90º the light does not cross the surface. Refracted Reflected

38. 10-Aug-15 Physics 1 (Garcia) SJSU Demo: Total Internal Reflection Prism demonstrates total internal reflection if the angle of incidence is large enough.

39. 10-Aug-15 Physics 1 (Garcia) SJSU Looking up Underwater Try this when you’re in the pool this summer Looking straight up you see the sky but outside the 96° cone surface is like a mirror

40. 10-Aug-15 Physics 1 (Garcia) SJSU Demo: Total Internal Reflection Past the critical angle all the light is internally reflected. Just below critical angle

41. 10-Aug-15 Physics 1 (Garcia) SJSU Fiber Optics Total internal reflection causes light to reflect inside a solid glass tube.

42. 10-Aug-15 Physics 1 (Garcia) SJSU The Big Picture The whole purpose of this course was to open your eyes to the universe. The most incomprehensible thing about the world is that it is at all comprehensible. Albert Einstein Camera obscura next to the Cliff House, San Francisco