My question is pretty brief. When two sound waves of nearly same frequencies interfere, we get beats.
But, I have not observed something like that happening in the case of light. In fact, most of the light around us is a collection of continuous wavelength range which must be all nearly same frequencies.
Can we observe beats in light waves, as in case of sound waves?
If yes, how to observe them?
Answer
The math of beats is absolutely the same for light as it is for sound, but ...
Most light around us in incoherent, so does not form beats on macroscopic time or distance scales.
It is hard to select to sources that could conceivable give visible beats Look at it this way the frequency of green light is around $ c /(500\text{ nm}) \approx 6 \times 10^{15} \text{ Hz} $. All the colors have frequencies of the same order of magnitude, so the beat frequencies of two randomly selected colors tend to be around $10^{13}$--$10^{14} \text{ Hz}$: much faster than your eye can detect. To construct a pair of sources that you could see beat would require controlling their frequencies to about 1 part in $10^{14}$. That's not easy.
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