Speed and wavelength
If waves are incident along the normal when passing from one medium to another, their speed and wavelength change but their direction does not change.
Image caption, Speed and wavelength
Waves incident along the normal and passing from deep to shallow water...
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The diagram below shows the refraction of waves passing from air to water (the equivalent of from deep to shallow).
As the waves travel from air to water, they slow down – water is denser than air.
They bend towards the normal and wavelength decreases.
The frequency of the waves remains unchanged.
| Property | Reflection | Refraction: deep to shallow | Refraction: shallow to deep |
| Speed v | unchanged | decreases (Slower) | increases (Faster) |
| Direction | i = r | Towards the normal | Away from the normal |
| Frequency f | unchanged | unchanged | unchanged |
| Wavelength λ | unchanged | decreases | increases |
| Property | Speed v |
|---|---|
| Reflection | unchanged |
| Refraction: deep to shallow | decreases (Slower) |
| Refraction: shallow to deep | increases (Faster) |
| Property | Direction |
|---|---|
| Reflection | i = r |
| Refraction: deep to shallow | Towards the normal |
| Refraction: shallow to deep | Away from the normal |
| Property | Frequency f |
|---|---|
| Reflection | unchanged |
| Refraction: deep to shallow | unchanged |
| Refraction: shallow to deep | unchanged |
| Property | Wavelength λ |
|---|---|
| Reflection | unchanged |
| Refraction: deep to shallow | decreases |
| Refraction: shallow to deep | increases |