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Waves

Light - Refraction.

A material is transparent if you can see through it.
If you can see through it, it means that light can travel through it.
Transparent materials include air, glass, Perspex, and water.

Light travels at different speeds in different materials
because they have different densities.
The higher the density, the slower light travels.
Light travels fastest in space (a vacuum) and a little slower in air.
Light moves noticeably more slowly in glass than in air
because glass is obviously more dense.

A line drawn at right angles to the boundary
between the two media (air and glass) is called a normal.

Light passing through Glass along a Normal

Light which enters a glass block along a normal does not change direction
but it does travel more slowly through the glass
and so its wavelength is smaller (continued).

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