Sound Wave
Light Sound and Waves

Light rays but not sound rays

Teaching Guidance for 5-11 11-14 Supporting Physics Teaching

Don't use the idea of rays in discussing sound

Teacher Tip: Rays are used to model light, but not sound.

Here is why.

In explaining the properties of light we suggest constructing diagrams based on light rays, which are imaginary. Rays can be imagined to represent infinitely thin beams of light.

In optics, light rays are used a lot because real light beams act in much the same way as the model rays. In other words, light really does travel along well defined paths, which do not diverge too much with distance.

Sound does not travel in sharply defined beams. Instead it spreads much more as it goes – beams are very hard to maintain.


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