Why do scientists think that light and sound are waves?
Sound waves and light waves change speed when they pass across the boundary between two substances with different densities, such as air and glass. This causes them to change direction and this effect is called refraction.
There is one special case you need to know. Refraction doesn't happen if they cross the boundary at an angle of 90° - in that case they carry straight on.
Remember that sound and light waves behave just like water waves in a ripple tank. The bending follows a regular pattern. Check your understanding of refraction by having a go at the animation.
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