instruments SM, Phy 123, Spring 2013 References and photo sources: - - PowerPoint PPT Presentation

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instruments SM, Phy 123, Spring 2013 References and photo sources: - - PowerPoint PPT Presentation

Jun 02, 2023 243 likes •609 views

Thin lenses and optical instruments SM, Phy 123, Spring 2013 References and photo sources: D. Giancoli, Physics for Scientists and Engineers, 3 rd ed., 2000, Prentice-Hall http://cvs.anu.edu.au (D. Denning and M. Kirk)

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Thin lenses and optical instruments

SM, Phy 123, Spring 2013 References and photo sources:

  • D. Giancoli, Physics for Scientists and Engineers, 3rd ed.,

2000, Prentice-Hall http://cvs.anu.edu.au (D. Denning and M. Kirk) http://www.ebiomedia.com NASA

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Power of lens measured in diopters

f P 1 

where f is focal length in meters Power is positive for converging lenses and negative for diverging lenses

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f d d

i

  • 1

1 1  

Lens equation: Magnification:

  • i
  • i

d d h h m   

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Sign convention is the tricky part, especially in multiple lens systems Convention from Giancoli p. 841:

  • Focal length is + for converging lens and - for diverging lens
  • Object distance is + if on the side of the lens from which the light is

coming (usual, unless in multi-lens system)

  • Image distance is + if on the opposite side of the lens from where

the light is coming, if on same side, image distance is –

  • Image distance is + for real images and – for virtual images
  • Height of image is + if image is upright and – if image is inverted.

Height of object is always taken to be +. Real image: rays actually pass thru image Virtual image: rays do not actually pass thru image

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Aberrations

Spherical aberration Chromatic aberration

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A bee’s eye view

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Anableps - minnow

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Magnifying glass

f N m    '

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Refracting telescope

40 inch refractor – Yerkes Observatory

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Reflecting telescope

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Keck Observatory

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Hubble Space Telescope

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Hubble space telescope 2.4 m primary mirror Launched in April 1990 Optics “repair” in 1993

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James Webb space telescope – 6.5 meter primary mirror Expected 2018 launch date

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From NASA: http://www.stsci.edu/jwst/science/sensitivity

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Compound microscope

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Camera

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Light vs. depth of field Shutter speed f-stop=f/D, each f-stop=factor of 2 in light intensity Faster the object or darker the day, need slower speed and/or larger D Larger D means narrower depth of field

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Speed limited on the low end by movement of

  • bject or support

platform (hand),

  • n high end by

technology and amount of light

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f-stop or f ratio Each stop differs by factor of 2 in light intensity Exposure goes as (time)(area opening) Amount of light goes as area, goes as diameter2 So, stops differ in diameter of sqrt(2)1.4 Aperture diagram for different f- stops If lens has a 10 mm focal length, an aperture of 5 mm would give f/2 Same lens with aperture of 1.8 mm would give f/5.6 Larger maximum aperture, more light, faster lens (usually more expensive … because more issues with controlling aberrations, I think)

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Aberrations

Apochromatic lens

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Aspheric lens

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Astigmatism