Light and Optics

Light and Optics

1. Light

   • History
     • Pythagoras
       • Thought we could see because light beams came out of our eyes.
     • Euclid
       • 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.
     • al-Haytham
       • Discovered how vision worked, and he was correct, unlike Pythagoras.
     • Newton
       • Using a prism, he discovered white light is a mixture of light of different colors.
     • Michelson
       • Discovered the speed of light.
   • Properties
     • Light travels in straight lines.
       • Called rays.
       • Represented by an arrow in diagrams.
     • Movement
       • Light can change directions
         • 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.
         • Refraction
           • When light bends through and object
             • Different objects and mediums refract light differently
     • Light is a form of energy
   • Sources
     • Natural
       • Sources in nature
         • bioluminescence, fire, sun, etc.
     • Artificial
       • Human made light sources
         • Light bulb, chemical reactions, etc.
   • Transmission
     • Passing through objects
       • opaque
         • Light is unable to pass through this object.
           • Creates shadows
             • Shadows are the absence of light
       • translucent
         • Light can partially pass through this object
       • transparent
         • Light can clearly pass through this object
           • ex. glass
     • Ray diagrams are pictures that show how light interacts with a given object
       • A mirror, lens, etc.
   • EM Spectrum
     • Spectrum of light
       • Catagorized by wave length
         • From longest to shortest: Radio, Microwaves, Infrared, Visible, Ultraviolet, X-ray, Gamma ray.
           • We can only see visible light

2. Optics

   • Devices
     • Man-made
       • Telescope
         • Reflecting
           • Uses concave mirror to focus light
         • Refracting
           • Uses convex mirror to focus light
       • Glasses
         • Uses either lense (depending on condition) to focus light on the retina of a slightly misshapen eye.
       • Contact lenses
         • Just like glasses, but directly on eye
       • Infrared camera
         • Complicated, uses mirror to reflect infrared light to detector.
     • Natural
       • Human eye
         • 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
     • Camera
       • Aperture
         • Diaphram
           • Shutter
             • Lens
               • film, light sensor array
                 • Color film
                   • Black and white film
   • Mirrors and lenses
     • Mirrors
       • Plane mirror
         • Just a flat mirror
       • Concave mirrors
         • shaped like a "cave", focus and collect light
       • Convex mirror
         • Opposite of concave
           • Spread light apart
     • Lenses
       • Double Concave
         • This lens focuses light rays as they pass through
       • Double Convex
         • This lens spreads light rays as they pass through

3. Other Facts about light

   • Lightyears are the distance light travels in a year
     • Good for measuring long distances in space

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