Spherical Mirrors

Lab reports due today • • • • Due at 5 pm. Turn in your notebook with your report. Bring to my office (119). Hand to me or leave in yellow box outside office. Spherical Mirrors • A reflective “portion of a sphere”. • If the mirror is a small enough portion, all light rays parallel to the principal axis (which passes through center C and the middle of the mirror A), will converge on a single focal point F. • The focal length f (distance from mirror to F) is half the radius of the sphere r. Figure 32.14 Object and Image distances • d0 = “object distance” = distance of object from mirror . • di = “image distance” = distance of image from mirror . • f = “focal length” = distance of F from mirror . • d0 is positive if the object is on the same side of the mirror as the incident rays. • di is positive if the image is on the same side of the mirror as the reflected rays. - di positive means image is “real and inverted”. - di negative means image is “virtual and upright”. • f is positive if incident rays parallel to the optic axis actually converge at F. - if F is on the side of the mirror where the reflected rays actually go. Concave mirror Figure 32.16 • Three rays leave one point on an “object”: 1) A ray parallel to the principal axis (aka optic axis), will pass through the focal point F. 2) A ray that passes through F, will end up parallel to the principal axis. 3) A ray that passes through C, will reflect back upon itself. • Where these three rays converge (or seem to converge), is the corresponding point on the image. Figure 32.17 Convex mirror Figure 32.19a Figure 32.19b Object and Image distances • d0 = “object distance” = distance of object from mirror . • di = “image distance” = distance of image from mirror . • f = “focal length” = distance of F from mirror . • d0 is positive if the object is on the same side of the mirror as the incident rays. • di is positive if the image is on the same side of the mirror as the reflected rays. - di positive means image is “real and inverted”. - di negative means image is “virtual and upright”. • f is positive if incident rays parallel to the optic axis actually converge at F. - if F is on the side of the mirror where the reflected rays actually go. 1 1 1   d o di f Figure 32.16 What is the radius of curvature of a plane mirror? 1)zero 2)infinity 3)it is equal to the length of the mirror Magnification • Ratio of image height to object height. An object is located 3 cm from the surface of a silvered spherical glass ball that is 3 cm in diameter. The image forms at which labeled point? When an object is closer to a concave mirror than the mirror's focal point, the 1) magnification is less than one. 2) image distance is negative. 3) image is inverted. 4) All of these are correct.