The YDSE apparatus is as shown in figure. The condition for point P to be a dark fringe is

Options

A. `(l_(1)-l_(3))+(l_(2)-l_(4))=n lamda`
B. `(l_(1)-l_(2))+(l_(3)-l_(4))=n lamda`
C. `(l_(1)+l_(3))+(l_(2)+l_(4))=((2n-1)lamda)/(2)`
D. `(l_(1)-l_(2))+(l_(4)-l_(3))=((2n-1)lamda)/(2)`

Answer

b

Explanation

For dark fringe,
Path difference `= (2n - 1) (lambda)/(2)`