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# In a Young's double slit experiment light of $\lambda =5000A^{\circ}$ is incident on two slits. At a point P on the screen the two rays arriving have a path difference of $1 \times 10^{-6} \;m$. If the central fringe (zero) is maxima . What is formed at p.

(a) First bright

(b) First dark

(c) Second bright

(d) Second dark

Path difference $=\delta =1 \times 10^{-6}$
$\qquad= 2 \times 5 \times 10^{-7}$
$\qquad= 2 \times 5000 \times 10^{-10}$
$\qquad =2 \lambda$
Since path difference is integral multiple $\lambda$ it is a bright fringe
Since $n=2$
Second bright fringe is formed
Hence c is the correct answer.