optics

• Refraction


  If the light ray meets the boundary between two mediums at a non-perpendicular angle, then there will be a sudden change in the direction of light when it transmits to the new medium
• Perpendicular transmission


  • If a light ray is travelling through one medium and then transmits into another, if the light ray meets the boundary at a perpendicular angle, then the light ray will not change directions
• Normal line


  An imaginary line that is perpendicular to the boundary between two mediums
• Incident ray


  The light ray in the starting medium
• Angle of incidence (θ1)


  The angle the incident ray makes with the normal line
• Refracted ray


  The light ray in the new medium
• Angle of refraction (θ2)


  The angle the incident ray makes with the normal line
• If light slows down

  It will bend towards the normal
• If light speeds up

  It will bend away from the normal
• Electromagnetic wave


  What light is
• Waves


  Transmit energy
• Types of electromagnetic waves

  • Non-ionizing (longer wavelength, lower frequency, lower energy)
  • Ionizing (shorter wavelength, higher frequency, higher energy)
• Radio


  Longest wavelength, lowest frequency, used for sending and receiving signals
• Microwave


  Effective at making water molecules vibrate, used to heat food
• Infrared


  Associated with heat, slightly less energetic than red visible light
• Ultraviolet


  Damages cells, used in tanning beds and nail salons
• 1. ray


  Used (in small doses) to get images of bones and teeth
• Gamma


  Very harmful, released from radioactive materials
• Visible spectrum


  Our eyes can detect light in the range of about 400 nm to 750 nm in wavelength, 4 x 10^14 Hz to 8 x 10^14 Hz in frequency
• Nanometer (nm)


  A billionth of a metre
• Shorter wavelengths


  Have more energy than higher wavelengths
• Ways objects interact with light

  • Incandescence (emitting light due to heat)
  • Electroluminescence (getting energy out of electricity used to create light)
  • Bioluminescence (a living thing using light)
  • Chemiluminescence (when a chemical reaction can generate light)
  • Fluorescence (when uv radiation is converted to visible light)
  • Phosphorescence (uv being stored and converted to visible light)
• White light


  When all visible wavelengths are concentrated into the same spot, our brains will translate it to "white"
• A red shirt looks red


  White light reflects on the shirt, the shirt reflects red wavelengths and absorbs other wavelengths, the reflected red light gets into our eyes
• Blue stained glass looks blue


  White light from the sun shines on the glass, only blue wavelengths are transmitted (let through), the rest are reflected outwards or absorbed
• Dispersion


  Light of different wavelengths refract at slightly different amounts, causing the different colours that comprise white light to spread out at slightly different angles
• Converging lenses


  • Use light rays to converge, light rays parallel to the principal axis will be transmitted through the lens such that they converge to a common point called the focal point (or focus)
• Locating objects with converging lenses


  Draw a ray from the top of the object to the center line of the lens parallel to the principal axis, draw a ray from the top of the object to the lens directly through the focal point, draw a light ray from the top of the object directly through the very center of the lens
• Diverging lenses


  • Use light rays to diverge, light rays parallel to the principal axis will be transmitted through the lens such that they diverge (spread out)
• Locating images with diverging lenses

  Draw a ray from the top of the object to the center line of the lens parallel to the principal axis, draw a ray from the top of the object to the mirror directly towards the focal point, draw a light ray from the top of the object directly through the very center of the lens
• Plane mirror


  When a light ray strikes a plane mirror, it reflects off it at the same angle that it hit it from, but on the other side
• Angle of incidence


  The angle between the incident ray and the normal line
• Angle of reflection


  The angle between the reflected ray and the normal line
• Virtual image


  The image you see of yourself appears to be on the other side of the mirror, there are no actual light rays behind the mirror
• Locating images through plane mirrors

  Draw a line from the object to the mirror, perpendicular to the mirror, measure this line, extend the line through the mirror by the same distance
• Concave mirrors


  • Parallel light rays coming "head on" to the concave mirror will all get reflected back through the focal point
• Locating images with concave mirrors


  Draw a ray from the top of the object to the mirror parallel to the principal axis, draw a ray from the top of the object through the focal point to the mirror, draw a light ray from the top of the object through the center of the mirror
• Convex mirrors


  • Parallel light rays coming "head on" to the convex mirror will all get reflected so that they can be back-traced to the focal point
• Locating images with convex mirrors


  Draw a ray from the top of the object to the mirror parallel to the principal axis, draw a ray from the top of the object to the mirror directly towards the focal point, draw a light ray from the top of the object to the mirror directly towards the center