Why the central rings in Newton rings exp are foemed by destructive interfrence?

The central rings in Newton's rings experiment are formed by destructive interference because the light waves reflecting off the top and bottom surfaces of a thin air film between a lens and a glass plate interfere with each other. At the center, where the air film is thinnest, the path difference between the two reflected waves is zero or an odd multiple of half the wavelength, leading to destructive interference and creating dark rings. As you move outward, the varying thickness of the air film causes alternating regions of constructive and destructive interference, resulting in a pattern of bright and dark rings.