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A point is situated at 7cm and 7·2 cm from two coherent sources. Find the· nature of illumination at the point if wavelength of light is 4000A.

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#### Solution

Path difference = 7.2 cm – 7 cm = 0.2 cm

`"Path diffrence "/lambda=0.2/(4000xx10^-8)=5000`

path difference is integral multiple ofλ

∴ It is bright point

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