What enables a convex lens to project an image onto a screen?
A convex lens is able to project an image onto a screen due to its ability to converge light rays. When an object is placed in front of a convex lens, the lens refracts (bends) the incoming light rays. The lens refracts the light in such a way that it converges the rays to a focal point beyond the lens.
By placing a screen or a photographic film at the focal point of the lens, the converging light rays form a real and inverted image on the screen. This image is formed as the light rays cross each other after passing through the lens. The size and location of the image depends on the distance between the object and the lens, as well as the focal length of the lens.