1. Reflection of Light

2. Reflectance u Light passing through transparent medium is transmitted, absorbed, or scattered u When striking a media boundary, light can also be reflected u Ratio of light reflected to light incident on surface is reflectance of surface

3. Types of Reflection u Diffuse: light reflected but scattered by irregular surface: paper, flat paint, snow u Regular (or specular): light reflected by polished surface without changing orientation between rays; images can be seen: shiny metals, mirrors, glossy paint, smooth water

4. Laws of Reflection u The angle of incidence is equal to the angle of reflection u The incident ray, the reflected ray and the normal to the surface are all in the same plane u True for regular and diffused reflection

5. Mirrors u Plane mirror: flat reflecting surface, usually a coating of silver on plane glass u Spherical mirror: small section of surface of sphere: can be convex or concave depending on which side is silvered

6. Image Types u Virtual Image: light rays don’t actually pass through image point but appear to have come from there u Real Image: formed by converging rays of light that actually pass through image point

7. Images Formed by Plane Mirrors u Always a virtual image, always upright (right side up) and same size u Reversed left and right u Appears as far behind mirror as object is in front of mirror u Thick mirrors can produce multiple images due to reflections at each boundary

8. Curved Mirror Terminology u Center of curvature: center of original sphere u Vertex: center of mirror u Principal axis: line drawn through center of curvature and vertex u Secondary axis: any line drawn through center of curvature to mirror

9. Curved Mirror Terminology u Principal focus: point on principal axis where rays parallel to principal axis converge, or appear to diverge from u Aperture: diameter of mirror u Focal Length: distance from principal focus to vertex

10. Converging (Concave) Mirrors u Converge or focus light u For light parallel to principal axis, light focused at principal focus u rays not parallel to principal axis are focused at a secondary focus u All focus points make up a focal plane u Focal length = 1/2 radius of curvature

11. Spherical Aberration u Large aperture mirrors exhibit spherical aberration where parallel rays don’t converge at same point u Can be corrected by making mirror parabolic u Parabolic reflectors used in flashlights, radio communication, car headlights, telescopes

12. Ray Diagrams u Used to locate and describe image produced by object/mirror combination u Draw principal axis, mirror, C and F, object u Draw any two of three important rays from point on object to mirror and along reflection

13. Ray Diagrams u Ray from object through F will reflect parallel to principal axis u Ray through C will reflect back on itself u Ray from object to mirror parallel to principal axis will reflect through F u For virtual images, use extensions of reflected rays drawn behind mirror

14. Ray Diagrams u Point where rays intersect is location of point on image corresponding to point on object u Usually use arrow for object; draw rays from point

17. Images of Concave Mirrors u Case 1: Object at infinite distance; incoming rays are parallel, focus at F; image is point u Case 2: Object farther than C; image is real, inverted, reduced, located between C and F u Case 3: Object at C; image is real, same size, inverted, at C

18. Images of Concave Mirrors u Case 4: Object between C and F; image is real, enlarged, inverted, located beyond C u Case 5: Object at F; all rays are reflected parallel, no image formed (reverse of case 1) u Case 6: Object closer than F; image is virtual, upright, magnified, behind mirror

19. Images of Convex Mirrors u Convex mirrors diverge light u Form only virtual, upright, reduced images, located between V and F behind mirror u Diverging mirrors have negative focal lengths because F is behind mirror

20. Mirror Equations u 1/f = 1/d o + 1/d i u h i / h o = d i / d o = Magnification u Focal lengths for convex mirrors are negative u Image distances for virtual images are negative

21. Mirror Equation