Two wavelengths of light — 590 nm and an unknown wavelength — illuminate a double-slit setup simultaneously, producing two overlapping fringe patterns. The central maxima of both patterns coincide at the same point. It is also observed that the 3rd bright fringe of the 590 nm light coincid

Question

Two wavelengths of light — 590 nm and an unknown wavelength — illuminate a double-slit setup simultaneously, producing two overlapping fringe patterns. The central maxima of both patterns coincide at the same point. It is also observed that the 3rd bright fringe of the 590 nm light coincides with the 4th bright fringe of the unknown light. What is the unknown wavelength?

Accepted Answer

442.5 nm. When the nth bright fringe of one wavelength coincides with the mth bright fringe of another, the path differences are equal: n * lambda1 = m * lambda2. Here n=3, m=4, lambda1=590 nm.

Solution

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