Particle model of reflection
Practical Activity for 14-16
Both particles and waves reflect in the same way as light.
Apparatus and Materials
For the class
- Glass block
- Bouncing ball
- Paper, white
- 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.
- 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.
- 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.
- 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