Today 2/5

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

6. focal length 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”

7. focal length focal length 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”

8. Converging Lens-Ray Diagrams d0object distance diimage distance Bend the ray at the middle of the lens In parallel-out through focus In through focus-out parallel Also straight through the center of the lens h0 hi f f The image will also appear on a screen placed at the image location.

9. Magnification equation Equations Thin lens equation f focal length always + for converging lens (- for diverging)d0 object distance + if on input sidedi 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 d0object distance diimage distance Bend the ray at the middle of the lens In parallel-out through focus In through focus-out parallel Also straight through the center of the lens h0 hi f f The image will also appear on a screen placed at the image location.

11. Converging Lens-Ray Diagrams d0 object distance image distance di Bend the ray at the middle of the lens In from focus-out parallel In parallel-out through focus Also straight through the center of the lens f f Now we have to “backtrack” the rays to see where they seem to come from!