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If I glow a white LED bulb and then put a color filter around it (for example, a red color filter or a violet color filter) , then will it change the frequency of light.

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The frequency will not be changed, but rather the color that is reflected/transmitted (depending on the nature of the filter). If you observe the white light THROUGH the filter and it appears to be red, then the filter either reflects or absorbs the other wavelengths while it lets the red ones through. The frequency you are observing are the same that was emitted by the diode, just that the rest of them have been scattered or absorbed elsewhere.

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  • $\begingroup$ To clarify: A white LED emits light which contains most of the visible colours. So there are photons of red, green, and blue. If you put a filter in between the LED and your eyes, the filter will abosrb (or reflect) some of those colours, letting only the red through. $\endgroup$
    – TanyaR
    Commented Sep 11, 2018 at 5:24
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The filter does not affect the frequency of the light; it just filters the light so that only the desired frequency (aka the "color" of the filter) is passed through. There is no change.

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