Light and sound waves - OCR 21st CenturySpeed of sound
Lenses are precisely shaped pieces of glass that have been developed and used in corrective glasses, telescopes, microscopes, binoculars, and magnifying glasses.
Sound waves change speed when they pass across the boundary between two substances with different densities. This causes them to be refracted.
The frequency of the sound wave does not change, but because the speed changes, the wavelength changes.
Sound obeys the same wave equation as light:
speed = frequency Ă— wavelength
There are not many everyday examples of refraction of sound. It is most commonly observed in situations where sound passes through a medium whose density gradually changes.
Sound waves often refract when passing over water. The air just above the water is cooler than the air higher up. As sound travels slower in the cooler air, the sound is refracted downwards towards the water.