20Concave Mirrors Summary Are a part of a sphereLight reflects from the inner surface.Images formed may be real or virtual.Depends upon object locationImages may be upright or inverted.Sometimes called converging mirrorsFocal length is positive.
21Important Terms Principal axis Image point Image distance (q) Object distance (p)Center of curvature CRadius of curvature RFocal point (F)Focal length (f)23.9
22Spherical AberrationSpherical aberration is an undesirable characteristic that is present in all spherical mirrorsIt may be eliminated by using parabolic mirrors.
24Ray Diagrams Front side and back side of the mirror Light rays are always in front of the mirror.This is taken to be the left side.
25Three Important RaysThe intersection of any two rays will locate the image.Parallel rays that come from infinity always pass through the focal pointWhen the object is at infinity, the image is at the focal point382, 188, 382, 383
35Convex Mirrors Summary Are a part of a sphereLight reflects from the outer surfaceImages formed are always virtualThey always lie behind the mirror.Images are always uprightSometimes called diverging mirrorsFocal length is negative
36Ray Diagrams for Convex Mirrors Front side and back side of the mirrorLight rays are always in front of the mirror.
37Ray Diagrams See Figure 23.11 Three important rays (see pg. 765) 23.11, 240, 384, 23.12
38Rays that come from infinity always pass through the focal point. When the object is at infinity, the image is at the focal point.
39The intersection of two rays will locate the image.
40Equations for Convex Mirrors These equations are the same as before.Magnification equationThe mirror equation
41Sign Conventions for Mirrors See Table 23.1 on page 765
42Applications of Convex Mirrors Side view mirrors on carsShoplifting mirrors
44Images Formed By Refraction Sign conventionsSee Table 23.2 on page 770
45Apparent Depth Flat refracting surfaces Apparent Depth (q) vs. Actual Depth (p)n1 is below the surface23.16, 243
46Atmospheric Refraction The Sun is not where it appears to be.It can be seen even though it is below the horizon.Sun dogs and Moon dogsHalos on cold winter days or nightsRefraction through hexagonal ice crystalsMirages23.21
47Thin LensesA thin lens is a piece of glass or plastic which is ground so that its surfaces are segments of either spheres or planes.A thin lens acts like two prisms.
48Refraction in Optical Instruments Thin lenses are used to form images by refraction in optical instrumentsCamerasProjectorsMicroscopesTelescopesBinocularsMagnifying glasses248, 249
49The Thin Lens EquationThe lens equation is virtually identical to the mirror equation.23.23
51Convex LensesConvex lenses form virtual images when the object is within the focal length of the lens.Example: a simple magnifying glass.Convex lenses form real images when the object is beyond the focal length of the lens.250
52Concave LensesConcave lenses never form real images
53Thin Lens Concepts Focal point (F) Focal length (f) 68 Thin lenses have two.Parallel light rays pass through the lens and converge or appear to originate here.Focal length (f)68
54Magnification Equation Equation for magnification:
59Ray Diagrams Ray diagrams (similar to mirrors) Three important rays Rays that come from infinity always pass through the focal point.When the object is at infinity, the image is at or appears to be at the focal point.The intersection of two rays will locate the image.247, 23.25, 69, 70
60Thin Lens Combinations The image formed by the first lens serves as the “object” for the second lens.256
61A location diagram is definitely useful when determining p2. 252
62Total Magnification of Thin Lens Combinations Formula:
63Spherical Aberration Similar to that produced by mirrors In mirrors, it can be reduced by using parabolic surfaces.Parabolic mirrors are used in headlights, satellite dishes, searchlights, and astronomical mirrors.Parabolic surfaces are more expensive to make.23.30
64In lenses, spherical aberration may be reduced by using a small aperture size.
65Chromatic AberrationChromatic aberration results because different wavelengths have different indices of refraction.Chromatic aberration is produced by lenses but not by mirrors.
66Chromatic Aberration may be reduced by using combinations of converging and diverging lenses made from different types of glassThis is expensive.