Light and Optics

Light
1. History
  1. Pythagoras
    1. Thought we could see because light beams came out of our eyes.
  2. Euclid
    1. Discovered the angles of reflection, and that they are the same for the incident ray and the reflected ray when you shine a beam of light at a mirror.
  3. al-Haytham
    1. Discovered how vision worked, and he was correct, unlike Pythagoras.
  4. Newton
    1. Using a prism, he discovered white light is a mixture of light of different colors.
  5. Michelson
    1. Discovered the speed of light.
2. Properties
  1. Light travels in straight lines.
    1. Called rays.
    2. Represented by an arrow in diagrams.
  2. Movement
    1. Light can change directions
      1. Reflection
        When light bounces off and object
        The law of reflections says that the angle of light hitting a mirror will be the same as the angle as it leaves.
        The incident angle is always equal to the reflecting angle.
      2. Refraction
        When light bends through and object
        Different objects and mediums refract light differently
  3. Light is a form of energy
3. Sources
  1. Natural
    1. Sources in nature
      1. bioluminescence, fire, sun, etc.
  2. Artificial
    1. Human made light sources
      1. Light bulb, chemical reactions, etc.
4. Transmission
  1. Passing through objects
    1. opaque
      1. Light is unable to pass through this object.
        Creates shadows
        Shadows are the absence of light
    2. translucent
      1. Light can partially pass through this object
    3. transparent
      1. Light can clearly pass through this object
        ex. glass
  2. Ray diagrams are pictures that show how light interacts with a given object
    1. A mirror, lens, etc.
5. EM Spectrum
  1. Spectrum of light
    1. Catagorized by wave length
      1. From longest to shortest: Radio, Microwaves, Infrared, Visible, Ultraviolet, X-ray, Gamma ray.
        We can only see visible light
Optics
1. Devices
  1. Man-made
    1. Telescope
      1. Reflecting
        Uses concave mirror to focus light
      2. Refracting
        Uses convex mirror to focus light
    2. Glasses
      1. Uses either lense (depending on condition) to focus light on the retina of a slightly misshapen eye.
    3. Contact lenses
      1. Just like glasses, but directly on eye
    4. Infrared camera
      1. Complicated, uses mirror to reflect infrared light to detector.
  2. Natural
    1. Human eye
      1. Pupil
        Opening that lets light in
        Iris
        Control Pupil size
        Eyelid
        Covers, protects eye
        Lens
        Focuses light
        Retina
        Detects light
        Cones
        Detect Color
        Rods
        Detects brightness, black, white
  3. Camera
    1. Aperture
      1. Diaphram
        Shutter
        Lens
        film, light sensor array
        Color film
        Black and white film
2. Mirrors and lenses
  1. Mirrors
    1. Plane mirror
      1. Just a flat mirror
    2. Concave mirrors
      1. shaped like a "cave", focus and collect light
    3. Convex mirror
      1. Opposite of concave
        Spread light apart
  2. Lenses
    1. Double Concave
      1. This lens focuses light rays as they pass through
    2. Double Convex
      1. This lens spreads light rays as they pass through
Other Facts about light
1. Lightyears are the distance light travels in a year
  1. Good for measuring long distances in space

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Light and Optics

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