Light, Sound and Waves

Light meeting obstacles

Physics Narrative for 5-11 11-14 Supporting Physics Teaching

Three possibilities

What happens when light travels through the air and meets the surface of an object, such as a table, mirror, window, or curtain? Various outcomes are possible.

Notice that all of the energy of the incident beam can only be shared out amongst the three possibilities: energy is conserved.

If the object is:

  • Opaque: no light is transmitted (the light is reflected and absorbed to varying degrees).
  • Translucent: some light is transmitted (the rest of the light is reflected and absorbed to varying degrees).
  • Transparent: ideally all light is transmitted (although in practice some light will be reflected and absorbed).

Notice that all the energy must be accounted for – energy is conserved.

is formalised by Law of Reflection
can be exhibited by Progressive Wave
has the special case Total Internal Reflection
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