# The figure shows a double slit experiment with P and Q as the slits. The path lengths PX and QX are nlambda and (n+2)lambda respectively, where n

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The figure shows a double slit experiment with P and Q as the slits. The path lengths PX and QX are nlambda and (n+2)lambda respectively, where n is a whole number and lambda is the wavelength. Taking the central fringe as zero, what is formed at X?

A. (a) First bright
B. (b) First dark
C. (c) Second bright
D. (d) Second dark

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For brightness, path difference =nlambda=2lambda
So second is bright.
I_(max)=(a_1+a_2)^2, I_(min)=(a_1-a_2)^2implies(I_(min))/(I_(max))=1/4