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Grading policy change:

Grading policy change:. Lowest HW score dropped. THIN LENS EQUATIONS: . converging. diverging. Example: An object 5 m away is focused at a point 2 m on the other side of a lens. What’s the focal length, type of lens, and magnification? .

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Grading policy change:

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  1. Grading policy change: Lowest HW score dropped

  2. THIN LENS EQUATIONS: converging diverging

  3. Example: An object 5 m away is focused at a point 2 m on the other side of a lens. What’s the focal length, type of lens, and magnification?

  4. Example: A lens has a focal length of -10 cm. Where’s the image formed of an object placed 20 cm to the left of the lens. What’s the type of lens and magnification? Is the image upright or inverted?

  5. Example: A lens has a focal length of +10 cm. Where’s the image formed of an object placed 8 cm to the left of the lens. What’s the type of lens and magnification? Is the image upright or inverted?

  6. LENS COMBOS The method: treat each stage separately!

  7. object

  8. A object Image A

  9. B Image A → Object for lens B

  10. Example 5 cm (1.5 cm tall) 12 cm fA= - 6 cm fB= + 4 cm Next …

  11. Example: Step 1 – find image formed by A (1.5 cm tall) 12 cm fA= - 6 cm Figure!

  12. Example: Step 1 – find image formed by A (0.5 cm tall) (1.5 cm tall) (-)4 cm 12 cm mA= +0.333 fA= - 6 cm Next …

  13. Example: Step 2 – Use this image as object for B 5 cm (0.5 cm tall) 4 cm mA= +0.333 fB= + 4 cm Next …

  14. Example: Step 2 – Use this image as object for B (0.5 cm tall) 4 cm 5 cm mA= +0.333 fB= + 4 cm Figure!

  15. Example: Step 2 – Use this image as object for B (0.50 cm tall) (1.5 cm tall) 4 cm 5 cm (+)7.2 cm (0.40 cm tall) mA= +0.333 fB= + 4 cm mB= -0.800 Overall magnification?

  16. Example: summary 5 cm (1.5 cm tall) 7.2 cm (0.40 cm tall) 12 cm mA= +0.333 fA= - 6 cm fB= + 4 cm mB= -0.800 mT = mA× mB= -0.2667

  17. Applications? Zoom lens (courtesy of Wikipedia)

  18. For lens assemblies in which the separation of lenses is much smaller than the focal length, we can pretend they’re both at the same position:

  19. step 1

  20. step 1 step 2

  21. step 1 If lenses are in same place! step 2

  22. Object position Final image position

  23. When two thin lenses are placed ‘together’, they act like a single lens whose focal length is given by Lens “power” ( Diopters D = m-1 )

  24. Opticians and eyeballs: ‘good’ eye: relaxed

  25. Opticians and eyeballs: ‘good’ eye: bulged

  26. Opticians and eyeballs: Far-sighted eye: relaxed Can focus distant objects by tensing lens, but not near objects

  27. Opticians and eyeballs: Far-sighted eye:

  28. example: what corrective lens is needed? converging

  29. Opticians and eyeballs: Near-sighted eye: relaxed Can’t focus distant objects by tensing lens, but cannear objects

  30. Opticians and eyeballs: diverging

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