Coherent sources...

Two sources of light are said to be coherent if the waves emitted from them have the same frequency and are 'phase-linked'; that is, they have a zero or constant phase difference.

Coherent source (laser)

Laser diagram Coherent light

Incoherent source

Monochromatic light Incoherent light

Materials Teaching Educational Resources
1999 MATTER Project, The University of Liverpool

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