Welcome to practical physicsPracticle physics - practical activities designed for use in the classroom with 11 to 19 year olds
 

Particle model of reflection

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

Weight and collision with block

 

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


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.


Teaching notes


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