In Young’s double slit experiment, the two slits act as coherent sources of equal amplitude A and wavelength l. In another experiment with the same set up the two slits are of equal amplitude A and wavelength l but are incoherent. The ratio of the intensity of light at the mid-point of the screen in the first case to case to that in the second case is:

• A. 1 : 2
• B. 2 : 1
• C. 4 : 1
• D. 1 : 1