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A Young's double slit setup with slits S1 and S2 is fully immersed in water (refractive index 4/3). The positions x of maxima formed on the water surface satisfy x² = p² * m² * lambda² - d², where lambda is the wavelength in air, 2d is the slit separation, and m is an integer. Find the value of p.

1. 1/2
2. 2/3
3. 3/2
4. 4/3

Correct answer: 3/2

Solution

Working through the geometry of path difference for maxima with the wavelength reduced by n in water, the coefficient p comes out to 3/2.

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