1. Optics The Swing, Pierre-Auguste Renoir Oil on canvas, 1876 How does this painting give evidence that light carries information? A Bar at the Folies-Bergère, Édouard Manet Oil on canvas, 1882 What distortions can you find in this painting that give it an unusual “feel?” click for applet

2. Mirrors and Reflection of Light Plane Mirror Conclusions Apparent path length of light equals actual path length of light Image size is the same as the object, therefore heights are equal, h o = h i Image orientation seems inverted horizontally (left/right), but is not. Incident angle equals reflected angle. Law of Reflection means θ i = θ r Image location (or distance) equals object distance, d o = d i Image type is virtual. Rays of light appear to diverge from image point, and cannot physically converge onto a surface. click for applet click for applet hoho hihi dodo didi

3. mirror object eye image eye θrθr θiθi Virtual Images A virtual image is formed when rays appear to diverge from a point. For a mirror, a virtual image will form behind the mirror, and it is upright. A virtual image cannot be cast onto a surface, but is seen in with the eye. click for applet click for applet

4. Reflection of Light click for applet Light always obeys the Law of Reflection but the surface irregularities (compared to the wavelength of light) determine whether the reflection is specular or diffuse. Multiple mirrors produce many reflections! click for applet

5. Real Images A real image is formed when rays actually converge to an point. For a mirror, a real image will form in front of the mirror, and it is inverted. A real image often appears on a surface, and then seen with the eye, but can also be viewed in a mirror. (A virtual image is only seen in a mirror) real image virtual image

6. Curved Mirrors CONCAVE MIRRORCONVEX MIRROR Light that reflects off a spherical mirror will not focus clearly. A smaller mirror, or a parabolic mirror, avoids spherical aberration. SPHERICAL MIRRORPARABOLIC MIRROR Some variables f = focal length F = focus (or focal pt) r = radius of curvature C = center of curvature

7. Ray Diagrams - Mirrors Principal Rays An incident ray parallel to the principal axis, reflects back through, or from, the focal point. An incident ray through, from, or towards the focal point, reflects back parallel to the principal axis. An incident ray through, from, or towards the center of curvature, reflects back along itself. click for applet click for applet click for applet click for applet

8. Mirror & Magnification Equation, Sign Conventions Note: magnification sign does not indicate image size. If |M| 1 image is larger. Sign conventions  Positive Negative object distance image distance focal length mirror type image height magnification REAL object, in front of mirror VIRTUAL object REAL image, in front of mirrorVIRTUAL image, behind mirror REAL focus, in front of mirror VIRTUAL focus, behind mirror CONVERGING or CONCAVEDIVERGING or CONVEX UPRIGHT INVERTED UPRIGHT INVERTED

9. anywhere virtual sameupright behind mirror | d i | = d o between mirror and F virtual largerupright behind mirror | d i | > d o between F and C real largerinverted in front, beyond C d i > d o at C real sameinverted in front, at C d i = d o beyond C real smallerinverted in front, btw F & C d i < d o anywhere virtual smallerupright behind mirror | d i | < d o Mirror Summary