Particle model of reflection
Both particles and waves reflect in the same way as light.
Apparatus and materials
For the class
Carbon paper, soft
Health & Safety and Technical notes
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.
a 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.
b 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.
1 Introduce these quick and simple experiments by asking,
Do particles reflect in the same way as light?
2 In step b 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.
3 After they have done the experiment, ask students to remember (from experimenting with a ripple tank) how waves behave on reflection.
4 Both particles and waves reflect in the same way as light.
This experiment was safety-checked in February 2006