The diagram gives a top view of a double slit interference experiment. L is a monochromatic light source with a vertical filament. B is a barrier containing two narrow vertical slits and S is a screen on which interference fringes are produced. The intensity is $I$ at the point on the screen where the centre of the fringe pattern is formed. What is the intensity, at that same point, when one slit is covered?
- A$\frac{I}{\sqrt{2}}$
- B$\frac{I}{2}$
- C$\frac{I}{2\sqrt{2}}$
- D$\frac{I}{4}$