Phys 115 1st Edition Lecture 16Outline of Last Lecture I. Magnetic force II. CurrentIII. SolenoidOutline of Current Lecture IV. ReflectionV. RefractionVI. Thin LensesCurrent Lecture- Ray model of lighto Light rays travel in a straight line until they encounter a change in mattero When they encounter a change in matter, they can be reflected or refractedo The speed of light depends on the index of refraction of the matter in which it travels v = c/n c = 3 x 108 m/s n = 1 for vacuum, n > 1 for mattero Light rays emanate from every part of an object and travel in all directions- Reflectiono Angle of incidence = angle incident ray makes with normal to the surfaceo Similarly for angle of reflection = angle of incidenceo True for curved as well as flat surfaces- Refractiono Occurs where N changeso True for curved as well as flat surfaceso Angles of incidence and refraction related by Snel’s lawThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.- Reflection at Flat Surfaceso A swim mask traps air between the glass and your eyes, so that light from outside the mask passes first through a flat layer of glass and then into air.o If surfaces are parallel, angle of incidence on second surface = angle of refraction on first surface.- Thin Lenseso Two refracting surfaces form a lens.o The optic axis of the lens is perpendicular to the lens surface and passes through its center.o A converging lens bends rays toward the optic axis; f> 0.o A diverging lens bends rays away from the optic axis; f< 0.o A lens has a focal point on each side.o Focal length depends on curvature and n- Ray tracing: converging lens, f > 0o Image location can be found by tracing at least two rays from the object.o Three rays are easy to trace:o Rays parallel to the optic axis are refracted through the far focal point.o Rays through the near focal point are refracted parallel to the optic axis.o Rays passing through the center of the lens do not bend.- Thin lens equationo 1/f = 1/s + 1/s’o Object distance s, image distance s’ and focal length f are relatedo f, s, or s’ can be positive or negativeo Magnification: s’ /
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