In YDSE, find the thickness of a glass slab `(mu=1.5)` which
should be placed in front of the upper slit `S_1` so that the central maximum now
lies at a point where 5th bright fringe was lying earlier (before inserting the
slab). Wavelength of light used is `5000 Å`.

Answer

5

Explanation

According to the question, shift = 5 (fringe width)
`:. ((mu - 1) tD)/(D) = (5 lambda)/(d)`
`:.t = (5 lambda)/(mu - 1) = (25000)/(1.5 - 1) = 50,000 Å = 5 xx 10^(-6) m`