wave interaction

• luminous - lets out its light, eg. sun
• reflection - an object that reflects light when it hits it.
• a more dense medium has a higher concentration of particles per unit volume than a less dense medium. light will be as close as possible to the normal line
• opaque - can't see through it, eg. paper - is very reflective
• concave lens - bend backwards. can't make a real image because the rays are diverging
• convex lens - bend inwards
• transparent - see through eg, window
• transmit (through a surface) - carry on through
• absorbed - energy stops being a wave and converts into something else
• white light from the sun has all the colours, but we can only see red, blue and green. because our cone cells can only detect red, blue and green. all the other colours are made from these three
• Yellow - red + green

  Magneta - blue + red

  Cuan - green + blue
• Refraction


  Waves travel through a medium or material
• Waves that can travel through a medium

  • Light waves
  • Air
  • Water
  • Any other transparent material
• Refraction


  • When a wave goes from traveling in one medium to another, refraction occurs
  • Refraction is a change in speed and direction of the wave
• Water waves go from deep to shallow water

  They slow down
• Water waves go from shallow to deep water


  They speed up
• Wave properties and refraction


  • Frequency does not change
  • Wavelength and speed can change
  • Direction of travel can change
• Optical density


  Transparent materials have different optical density from each other
• Light waves travel in a medium

  They travel more slowly in a denser medium and faster in a less dense medium
• In empty space the speed of light is 3.00x10^8 m/s
• Change in speed of light

  Causes the direction of the wave to change compared to the normal line
• Light Refraction rules


  1. If light travels from less dense to more dense medium:

  2. Slow down

  3. Change direction toward the normal line

  4. If light travels from more dense to less dense medium:

  5. Increase speed

  6. Change direction away from the normal line
• Luminosity


  Luminous objects produce their own light, which radiates away in all directions
• Luminosity


  • The glow can be a result of being high temperature, or due to energy released in a chemical reaction
• Reflectivity


  Reflective objects appear when light from another source shines upon them
• All visible non-luminous objects are at least a little bit reflective
• Reflectivity


  The more reflective, the brighter they appear
• Ray diagrams


  Rays represent the path a single light wave takes after it is emitted until it is absorbed
• Ray diagrams


  • The ray is shown as a straight line with an arrowhead showing the direction of the light's motion
  • Rays always start from luminous objects, but they can bounce off reflective objects along the way
• Law of reflection


  angle of incidence = the angle of reflection
• Formation of an image


  Multiple rays reaching the eye from slightly different directions allow the eye to see the shape and size of objects in the field of view
• Real image


  If the rays come directly from the object seen
• Virtual image


  If the rays' direction is changed along the way
• Specular reflection


  Smooth flat planar surface are able to reflect multiple rays at once, so that parallel incident rays become parallel reflected rays
• Specular reflection


  The parallel rays will produce a clear image for the observer
• Diffuse reflection


  Rough surfaces reflect all the same rays, but the rays which became parallel will not be parallel upon reflecting
• Diffuse reflection


  The nonparallel rays will carry light but no clear image