Presentation on theme: "Created by Stephanie Ingle Kingwood High School"— Presentation transcript:
1 Created by Stephanie Ingle Kingwood High School Refraction & LensesCreated by Stephanie IngleKingwood High School
2 Snell’s Lawnormalincident rayAir (n=1.0003)1n = index of refraction for medium (no units)Boundaryreflected ray2Water (n= 1.33)Angles are always measured from the normal, never the surface
3 Index of Refraction Light changes speed (v) as it enters a new medium In a vacuum the speed of light (c) is 3.0 x 108m/sThe index of refraction (n) of a material is the ratio of the speed of light in a vacuum to the speed of light in the material.Index of refraction has no units!
4 Critical AngleThe incident angle of light that causes refraction along the boundary between surfacesThe angle of refraction will always be 90oOnly possible when going from more optically dense (high index of refraction) to less optically dense medium (low index of refractionOnly possible when light speeds up as it passes through the boundaryn=1r=900cn=1.5
5 Total Internal Reflection When incident light strikes a boundary at an angle greater than the incident angle it does not cross the boundary into the new medium.Instead, all of the light is reflected from the boundary back into the original medium according to the Law of Reflection.
6 Concave Lenses Thicker at the edges than in the center Parallel rays of light from a far object will refract throught the lense and diverge as if they came from the focal point.Concave lenses also called “diverging lenses”Light may come in from either side of lens so there will be a focal point on both sides equal distances from the lens (assuming symmetrical lenses).
7 Convex Lenses Thicker in the center than at the edges Parallel rays of light from a far object will refract through the lens and converge at the focal point.Convex lenses also called “converging lenses”Light may come in from either side of lens so there will be a focal point on both sides equal distances from the lens (assuming symmetrical lenses).
8 Calculations f = focal length do = object distance di = image distance hi = image heightho = object heightM = magnification
9 Interpreting Calculations Focal length (f)converging, then f = + diverging, then f = -Image distance (di)di=+ , then image is realdo= -, then image is virtualMagnification (M)M = +, image is erectM = - , image is inverted
10 Ray Diagram Convex Lens Image is real, inverted, & reduced Draw 3 rays from tip of object:1) parallel, then through f2) through f, then parallel3) through the lens at the principal axisImage is real, inverted, & reducedff
11 Ray Diagram Convex Lens (Inside f) Draw 3 rays from tip of object:1) parallel, then through f2) from same side f, through tip of object, then parallel3) through the lens at the principal axisimageffobjectImage is virtual, erect, & magnified
12 Ray Diagram Concave Lens Image is virtual, erect, & reduced Draw 3 rays from tip of object:1) parallel, then refracted ray from f on same side of lens2) to lens along a line that would pass through f on the other side of lens, then parallel3) through the lens at the principal axisconcave lens (axis)objectimageffImage is virtual, erect, & reduced
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