The heart of quantum mechanics – Many photons at the single- and double slit

Let us compare the interference pattern of the single slit with that of the double slit.

Firstly, after opening the second slit, we see more minima and maxima.

Secondly, at point P, the light intensity on the screen in case of a double slit decreases compared to the single slit.

Thirdly, the light intensity in the centre of the screen is higher in case of the double slit.