[" In Young's double slit experiment,the two slits act as coherent sources of equal amplitude "A" and "],[" wavelength "lambda" .In another experiment with the same setup the two slits are sources of equal amplitude "A" and "],[A" and wavelength "lambda" but are incoherent.The ratio of the average intensity of light at the midpoint of "],[" the screen in the first case to that in the second case is:- "],[[" A) "1:1," (B) "2:1," (C) "4:1," (D) none of these "]]