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Announcements 3/14/11

Announcements 3/14/11. Prayer Exam is being picked up from Testing Center even as we speak, hopefully graded within a couple of days. Thought question. I look at my image in a round Christmas ornament. Which of the following will be true? The image will be upright (not inverted) and real.

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Announcements 3/14/11

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  1. Announcements 3/14/11 • Prayer • Exam is being picked up from Testing Center even as we speak, hopefully graded within a couple of days

  2. Thought question • I look at my image in a round Christmas ornament. Which of the following will be true? • The image will be upright (not inverted) and real. • The image will be upright and virtual. • The image will be inverted and real. • The image will be inverted and virtual. • Can’t say… it will depend on where you (the object) are relative to the focus.

  3. Reading Quiz • A converging lens should be: • convex • concave

  4. Convex/converging Lens at each interface, Snell’s law is satisfied f if not parallel, they converge (image formed) at a different point parallel rays converge to the focal point

  5. The equation: Where will image be formed? focus focus Ray diagram just like one for concave mirror, except rays continue to right instead of reflecting back! Magnification same: positive q = right hand side of lens

  6. Concave/diverging Lens f parallel rays seem to be coming from the focal point

  7. The equation: Diverging lenses virtual image! (negative f) Negative q: means image on same side of lens as object (virtual)

  8. Demos • Demo: “Real image or not?” Class poll: What kind of image is this? • Real • Virtual

  9. Sign conventions: summary • Assuming that the light rays are coming from the left:

  10. Reading Quiz • When you look straight down at an object under water, it appears to be ____________ than actuality. • closer to you • farther from you

  11. Thick lenses and surfaces Careful with signs!!! (see table 36.2) Lens-makers’ eqn:

  12. Thought question • Can a converging lens ever produce a virtual image? • Yes • No

  13. Thought question • What happens if I cover up the upper half of lens? • Nothing • Upper half of image disappears • Lower half of image disappears • Intensity of image goes down by 50%

  14. Thought question • Can a diverging lens ever produce a real image? • Yes • No

  15. Multiple element problems • Image of one becomes object of next • Worked problem: Find qfinal, Mtot f = 20 cm f = -60 cm 60 cm 15 cm Answers: image is 20 cm to right of -60cm lens; M = -0.67

  16. Rest of time: class-designed problems • p = _____ • f = _____ • ray diagram = ? • q = ? Including some with these converging lenses, which we have: f = +8.05 cm f = +9.34 cm f = +17.0 cm f = +20.8 cm f = +45.0 cm

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