The figure shows two points sources which emit light of wavelength ​λ in phase with each other and are at a distance d = 5.5 ​λ apart along a line which is perpendicular to a large screen at a distance L from the centre of the source. Assume that d is much less than L.Which of the following statement(s) is/are correct 

(A) Only five bright fringes appear on the screen
(B) Only six bright fringes appear on the screen
(C) Point y = 0 corresponds to bright fringe
(D) Point y = 0 corresponds to dark fringe.

Dear Student
since the two sources are coherent and are in phase we can assume the case to be as in young's double slit experiment
given d= 5.5λ
we know d sinθ =(n)​λ for n=1,2,3.... for bright fringe
d sinθ =(n+1/2)​​λ ; n=1,2,3...... for dark fringe
at the max fringe ​sinθ =1
thus d/​​​​λ =5.5= n+1/2
= n = 5; hence max number of  dark fringes =5
and at central point y=0 a dark fringe is formed while two dark fringes are formed on either side of central fringe 

Answer: option A,D


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Ans: Option C
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