Visible Light Waves

• law of reflection: angle of incidence = angle of reflection
• angle's are counted relative to the normal, which is a perpendicular drawn from the reflecting surface at the point of incidence
• image formed by a plane mirror is always:

  1. same size as object
  2. same distance behind mirror as in front of it
  3. upright (same as object)
  4. back-to-front (lateral inversion)
  5. virtual
• virtual image is formed where light rays only appear to come from and cannot be cast onto a screen
• refraction occurs when a wave changes speed as it passes from one region to another
• refraction usually causes wave direction to change, such as when ocean waves go from a deeper to shallower region and light passes through glass from air
• less to more optically dense transition: air bends toward normal, angle of incidence greater than angle of refraction
• more to less transition: air bends away from normal, angle of refraction greater than angle of incidence
• why do pools appear shallow?

  because as the light rays leave the water, refraction occurs due to the more to less optically dense transition and the angle of refraction leads to a change to the perceived position due to the perceived source of light rays being closer (i dont like this explanation)
• n = sin i / sin r
• for glass refractive index experiment just use apparatus, measure constant intervals of values int able, plot sin i (y axis) against sin r (x axis), the gradient is the refractive index
• dispersion is when a prism splits white light into spectrum
• the refrective index of glass or perspex of a prism varies with colour of the spectrum that make up light, violet has the highest and red has to lowest refractive index
• total internal reflection occurs when:

  1. light is incident on a boundary between optical more to less dense substance
  2. angle of i greater than critical angle for interface
• n = 1 / sin c
• if angle of incidence = critical angle, refraction 90 degrees and partial reflection
• no refraction and total internal reflection occurs when angle of incidence greater than critical angle