In Young's double-slit experiment, the point source is placed slightly off the central axis shown in Fig. 2.45.
a. Find the nature and order of the interference at point P.
b. Find the nature and order of the interference at point. O.

Explanation

a. As discussed in pervious case, here `b = 1 mm, d = 10 mm, a = 1 m`, and `D = 1 m`
Using Eq. (i) for path difference between the waves reaching at point P,
`Delta x = (1.10)/(10^(3)) + (5 xx 10)/(2 xx 10^(3)) m = 35 xx 10^(-3) mm`
If it is maximum at point P, then `Delta//lambda` will be an integer, i.e.,
`(35 xx 10^(-3))/(500 xx 10^(-9) xx 10^(3)) = 70`
A maximum of order 70 occurs at P.
b. At O, `Delta x'_(0) = (1 xx 10)/(10^(3)) = 10 xx 10^(-3) mm`
`implies (Delta x )/(lambda) = 20`
Hence, maximum of the order 20 occurs at O.