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What are coherent sources of light? Why are coherent sources required to obtain sustained interference pattern? |
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Answer» The sources of light, which emit continuous light waves of the same wavelength, same frequency and in same phase or having a constant phase difference are called coherent sources. When there is a single source of light, the distribution of light energy in the surrounding medium is uniform in all the directions. But, when we have two coherent sources of light emitting continuous waves of same amplitude, same wavelength and in the same phase (or with a constant phase difference), the distribution of light energy does not remain uniform in all the directions. At some points, where the crest of one wave falls on crest of the other, resultant amplitude is maximum. At certain other points, crest of one wave falls on trough of the other; and resultant amplitude becomes minimum (zero). This modification in energy distribution due to coherent sources gives rise to sustained interference pattern. |
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