The optical path difference between two identical waves arriving at a point is `371 lambda`. Is the point bright or dark ? If the path difference is `0.24 mm`, calculate the wavelength of light used.

Explanation

Given : Path difference `= 371 lambda`
Path differences is an even multiple of `(lambda)/(2)`.
Hence, the point will be bright,
Path difference `= 37 lambda = 0.24 xx 10^(-3) m`
`:. lambda = (0.24 xx 10^(-3))/(371)`
`= 6.469 xx 10^(-7) m`
`lambda = 6469Å`