Converging and Diverging LensesLenses are used to focus light and form images.There are a variety of possible types We will consider only the symmetric onesthe double concave and the double convex.12Converging at the Focal PointFor a double convex (i.e. converging) lens, the light refracts such that it converges at the focal point.
23Diverging from the Focal PointA double concave (i.e. diverging) lens has the refracted rays diverging as if they all come from the focal point.
344Constructing Ray DiagramsDraw two of the three principal rays originating from the same point on the object and follow these rules:
1. P-Ray is drawn through a point on the object and parallel to the principal axis. It is refracted through the focal point, F.
2. F-Ray is drawn through a point on the object and through (convex) or towards (concave) the focal point. it is refracted parallel to the principal axis.
3. V-Ray is drawn through a point on the object and through the vertex. It goes straight through and does NOT change direction (assuming lens is thin)45Rays Converging Lens
56Image Types Converging LensConverging = ConvexThe convex lens forms different image types depending on where the object is located with respect to the focal point
5 possible object locationsCase 1: The object is located in front of FCase 2: The object is located at 2FCase 3: The object is located beyond 2FCase 4: The object is located between F and 2FCase 5: The object is located at F, the focal point.
Please complete handout for CONVEX lenses (front half)(two examples are done for you on the next slides to help get you started)67Image Types Converging LensCase #1: Object is Located in front of F
Notice that you refract the ray along the optic axis i.e. the middle of the lens7Image Properties in front of FL
T - Same side of lens as object
VirtualNotice here that for location, you are telling me what SIDE of the lens the image is on (same side or opposite side as the object)89Ray Diagram - Converging LensCase #2: Object is Located at 2F
9Image Properties at 2FL
T - At 2F Opposite Side
Real Notice here that for location, you are giving an approximate location (between __ and ___, or at ____), but you are also telling me what SIDE of the lens the image is on (same side or opposite side as the object)1011Rays Diverging Lens
Diverging = CONCAVE1112Ray Diagram - Diverging Lens
Locate the image of an object located between F and 2F for a diverging lens12Diverging LensesComplete the ray diagrams for concave/diverging lensesYou only need to complete two or three of these if you catch on to the trend, you can stop!1313Complete the summary table for Image properties of Diverging and Converging (next slide)14Summary: Image Characteristics formed by Concave and Convex LensesConcave Lens (Diverging)Object LocationSizeAttitudeLocationTypeArbitraryConvex Lenses (Converging)Object LocationSizeAttitudeLocationTypeBeyond 2FAt 2FBetween F and 2F
In front of F
Click here to load reader