Are they the same?
Is dispersion only to do with light waves & diffraction for all waves?
The are different unrelated phenomena.
Dispersion occurs when the "velocity" of light in a material depends on the wavelength. Thus different wavelengts of light are spread out upon emerging from the material.
Difraction occurs when superpostion of phase related light waves cause variations in intensity.
Besides, these are features present in a lot of different wave types, not only light waves (water waves is a good example).
Note that not only can we have the wavelength-dispersion mentioned by Integral, but also amplitude-dispersion
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