Refraction
Light, Sound and Waves

Particle model of reflection

Practical Activity for 14-16 PRACTICAL PHYISCS

Demonstration

Both particles and waves reflect in the same way as light.

Apparatus and Materials

For the class

  • Glass block
  • Bouncing ball
  • Marble
  • Paper, white
  • Carbon paper, soft

Health & Safety and Technical Notes

Read our standard health & safety guidance


The block may be so massive that it does not move on collision. If not, place a large weight behind it or fix it to the bench with a G-clamp.

Procedure

  1. One student bounces a ball on the floor, at various angles, across a short distance to a partner. The paths before and after collision are in a vertical plane.
  2. A student rolls a marble along a table (in a horizontal plane) to gently bounce against a vertical surface of a glass block. Repeat the experiment at different angles of incidence.

Teaching Notes

  • Introduce these quick and simple experiments by asking,
  • "Do particles reflect in the same way as light?"
  • In step 2 you can record the path of the marble before and after hitting the wall by placing a sheet of carbon paper over a sheet of plain paper on the table. Ask students look for a pattern in the angles. It is easy to see the symmetry of the situation, even if angles of incidence and reflection are not mentioned.
  • After they have done the experiment, ask students to remember (from experimenting with a ripple tank) how waves behave on reflection.
  • Both particles and waves reflect in the same way as light.

This experiment was safety-tested in February 2006

Refraction
can be represented by Ray Diagrams
formalised by Snell's Law
has the special case Total Internal Reflection
is used in analyses relating to Lens
can be analysed using the quantity Refractive Index
can be exhibited by Progressive Wave
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