Refraction

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Refraction

• Marcus Han 3O3 (10)

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Refresh

• Refraction is the change in direction of a wave/
  light ray when it enters an optically
  denser/lighter medium at an angle.

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1. Microscope

• Light bounces off the mirror, passes through the
  specimen on the stage and into the objective
  lenses. They refract of the light beams so that
  they travel straight through the microscope tube.
  When they reach the eyepiece lenses they are
  refracted into our eyes.

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• Different colours of light are refracted more
  than others. This is known as chromatic
  aberration.
• Chromatic pertaining to color or colors
• Aberration (optics) any disturbance of the rays
  of a pencil of light such that they can no longer
  be brought to a sharp focus or form a clear
  image
• To prevent this, most microscopes use more than
  one lens for the objective and the eyepiece.

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2. Refractor telescope

• There are 2 types of telescopes the reflector
  telescope and the refractor telescope.

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• The objective lens makes light rays converge at a
  focal point in the telescope to collect a bright
  image. It is then magnified to the size of a
  pupil and the eyepiece brings this bright image
  to the eye.
• This magnification allows the image to take up a
  lot of space on the retina so we will be able to
  see distant objects very clearly.

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3. SLR (Single Lens Reflex) Camera

• When the shutter opens, light rays enter the
  lens.
• An image formed by a single converging lens would
  be affected by aberrations like chromatic
  aberration.
• By using several lenses made of different
  materials, each lens handles colors in a certain
  way to make the colours realign when the lenses
  are put together.

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• The converging lens make the light rays converge
  at a point to form a bright image, which is
  exposed to film. The film makes a chemical record
  of the pattern of light, with loads of tiny
  light-sensitive grains, spread out in a chemical
  suspension on a strip of plastic. When exposed to
  light, they undergo a chemical reaction.

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Shutter

• Controls how long the film is exposed to the
  light.
• Most SLR cameras use a focal plane shutter which
  consists of two "curtains" between the lens and
  the film. When a picture is taken, the first
  curtain slides open. After a while the second
  curtain slides in from the other side to stop the
  exposure.

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• The curtains are controlled by a complicated set
  of gears, springs and switches.

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4. Nuclear reactors (utilising Cherenkov
radiation)

• Named after Pavel Alekseyevich Cherenkov
• When charged particles pass through an insulator
  at a constant speed greater than the speed of
  light in that medium,
• They polarise the molecules of that medium, which
  quickly return to their ground states, causing
  immediate radiation.
• This is called Cherenkov radiation and it causes
  the blue glow in nuclear reactors.

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5. Phoropter

• An instrument to measure a persons refractive
  error and determine prescriptions for spectacles.
  The patient sits behind the phoropter, and looks
  through a pair of lenses. The optometrist changes
  lenses on the phoropter according to the patients
  feedback on which lenses give the best vision.
• In a pair of spectacles/ a phoroptor the lenses
  compensate for refraction error by moving the
  blurred images of distant objects backward onto
  the retina.

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References

• http//www.yesmag.ca/how_work/microscope.html
• http//science.howstuffworks.com/telescope1.htm
• http//dictionary.reference.com/browse/chromatic
• http//dictionary.reference.com/browse/aberration
• http//static.howstuffworks.com/gif/camera10.jpg
• http//electronics.howstuffworks.com/camera4.htm
• http//electronics.howstuffworks.com/camera3.htm
• http//electronics.howstuffworks.com/camera2.htm
• http//static.howstuffworks.com/gif/camera11.jpg
• http//en.wikipedia.org/wiki/Pavel_Alekseyevich_Ch
  erenkov
• http//en.wikipedia.org/wiki/Cherenkov_radiation
• http//upload.wikimedia.org/wikipedia/commons/b/b8
  /Cerenkov.jpg
• http//www.thecomputerschool.net/modules/internet/
  images/IE_toolbar_clip_refresh.gif
• http//upload.wikimedia.org/wikipedia/commons/1/13
  /FC3A9nytC3B6rC3A9s.jpg
• http//rainbowboys.blogspot.com/2010/03/cherenkov-
  radiation.html
• http//3.bp.blogspot.com/_n6urvItzBdQ/S43kd4LwmuI/
  AAAAAAAAsoE/C1rLBlNhnCw/s1600-h/Advanced_Test_Reac
  tor.jpg
• http//0.tqn.com/d/vision/1/0/P/-/-/-/phoropter2.j
  pg
• http//vision.about.com/od/eyeexaminations/ig/Eye-
  Exam-Equipment/phoropter.htm