1. Today 2/5  Images and Lenses  Lab: Any Questions?  Start reading chapter 26.6-8 on Lenses  HW:2/5 “Converging Lens” (3 pages) Due Friday, 2/7  Exam IThursday, Feb 13

2. This Week’s Lab Pins “Images” will not line up when the “objects” do

3. This Week’s Lab Pins “Objects” will not line up when the “Images” do

4. Lenses -- Wave Picture A converging lens bends light toward the axis

5. Lenses -- Ray Picture A converging lens bends light toward the axis like a prism ? n = 1.5 n = 1.0 “Thin Lens” approximation assumes a single bend at the midline.

6. Converging Lenses A converging lens bends light toward the axis Focal point is the place on the axis where all rays arriving parallel to the axis are directed “In parallel-out through focus” focal length

7. Converging Lenses Focal point is the place on the axis where all rays arriving parallel to the axis are directed There is a second focal point on the input side where all rays directed away from it leave parallel to the axis “In through focus-out parallel”“In parallel-out through focus” focal length

8. Converging Lens-Ray Diagrams ff Bend the ray at the middle of the lens In parallel-out through focus Also straight through the center of the lens d i image distance d 0 object distance The image will also appear on a screen placed at the image location. h0h0 hihi In through focus-out parallel

9. Equations Thin lens equation Magnification equation f focal length always + for converging lens (- for diverging) d 0 object distance + if on input side d i image distance + if output side (- if on input side) m magnification + if image is (- if image inverted) h height + if not inverted (- if inverted)

10. Converging Lens-Ray Diagrams ff Bend the ray at the middle of the lens In parallel-out through focus Also straight through the center of the lens d i image distance d 0 object distance The image will also appear on a screen placed at the image location. h0h0 hihi In through focus-out parallel

11. Converging Lens-Ray Diagrams ff Bend the ray at the middle of the lens In from focus-out parallel Also straight through the center of the lens d 0 object distance image distance d i Now we have to “backtrack” the rays to see where they seem to come from! In parallel-out through focus