Physics

• Luminous


  Gives off light
• Translucent


  Some light is blocked
• Opaque


  All light is blocked
• Transparent


  No light is blocked
• Light


  Travels in straight lines at 300 000 000 m/s
• Seeing luminous objects


  1. The light travels in a straight line from luminous objects

  2. The light enters your eyes
• Seeing non luminous objects

  1. Light shines from a non luminous object
  2. It is then reflected off an object
  3. The light then enters our eyes
• Shadows

  1. A luminous object’s light hits an opaque object at a straight line
  2. The absence of light behind the opaque object is a shadow
• Angles of incidence and reflection

  The angle of incidence is the same as the angle of reflection
• Angles of incidence and reflection

  θi (incidence) =θr (reflection)
• How to measure angles

  Measure angles from the normal line
• Convex vs Concave

  Convex mirrors are used to spread out light, and concave mirrors are used to focus light
• Refraction

  Refraction is:

  The change in the speed of a wave, due to a change in material, that results in a change of direction
• Refractive index

  Refractive index= 3x10^8 / speed in material
• TIR

  Total internal reflection occurs when a wave reflects off the inside of a surface.
• Uses of TIR

  Fibre optic cables use TIR. Light travels through thin and solid plastic wires
• Different angles

  TIR, critical angle, refraction

  
• Dispersion

  Dispersion is when different colours refract through different amounts
• What happens to light when it refracts?

  1. The light bends
  2. The light slows
• Define refractive index

  The measure of the bending of a light when passing from one medium to another
• What is the colour of an object determined by?

  1. The colour it reflects
  2. The colour of the light shining on it
• Filters

  A blue filter only lets through (transmits) blue light, the rest is absorbed.

  
• What do filters do?

  Change the colour of the light
• What are the primary colours of light?

  Red, green, blue
• Parts of the eye

  
• Parts of the eye

  Iris changes the size of the pupil Cornea allows light through

  Ciliary muscles change the shape of the lens, relaxed= thin and focused on distant objects, contracted= thick and focused on near objects

  Pupil controls how much light enters the eye

  Lens refracts and focuses light

  Retina is where the image is formed and is converted to electrical impulses

  Optic nerve sends electrical impulses to the brain