What travels and what doesn't travel?
Teaching Guidance
for 5-11
11-14
Sound as a disturbance in the air
Wrong Track: The air just in front of the loudspeaker is pushed forward by the cone and it then travels to your ear so that you can hear the sound.
Right Lines: Vibrations travel as the disturbance from the speaker cone spreads out through the air. First of all the air next to the cone is made to move to and fro. Since neighbouring particles affect one another this pattern is passed on to groups of particles all around. So the pattern of vibration travels from one block of particles to the next, and the sound travels without the particles needing to make the trip themselves.
Vibrations travelling
Thinking about the learning
Some children have the idea that sound is an entity that itself travels from speaker to ear. This view needs to be countered with the scientific view that sound is not an object but a process – the travelling disturbance of the medium.
Thinking about the learning
The fact that sound travels through solids, where the particles are restricted to vibrating about fixed positions, provides a good counter-argument to those who think that the particles need to move from source to detector in order to carry the sound.
