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AS Physics

Why are two coherent sources of waves needed to observe interference?

coherent waves have the same wavelength and so can undergo constructive or descructive interference fully. if they have different wavelengths they will not be able to fully cancel or add. can't quite explain why in words so I'd use a diagram showing that you wouldn't get frings and how the wavelengths are different.

Reply 2

Jonatan

The Chameleon

Why are two coherent sources of waves needed to observe interference?

It is actually possible to observe interference phenomena from non-coherent light sources. The rainbow pattern you can see in any CD/ DVD is an example. Coherent light is however useful in several applications were the fact that th light is perfectly in pahse allows you to study rather complicated optical phenomena with relatively simple equipment. As an example, creating a hologram that is visible when illuminated by coherent light can be done with normal photographic equipment and a laser beam. To create a hologram that works with non-coherent light, however, requires a more elaborate setup.