Sagot :
Option-1,3 1. Not monochromatic sources. - interference is due to two monochromatic sources,3. observed from a distance similar to or smaller than the separation between the sources. -
Monochromatic radiation is electromagnetic radiation having a single, fixed frequency in physics. The term monochromatic light is frequently used when that frequency is a component of (or close to) the visible spectrum. The human eye recognizes spectral color in monochromatic light.
Monochromatic radiation has a single wavelength that never changes when it moves through a vacuum or a uniform transparent medium.
Because of the Fourier transform's localization property, no radiation can be completely monochromatic because that would need a wave with an endless length (cf. spectral coherence). Even from lasers or spectral lines, "monochromatic" radiation in reality always consists of components with a range of frequencies of non-zero breadth.
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