Why is it that the lenses of a camera is circular while the picture that comes out is a rectangle?

The shape of the image created by a lens isn't affected by the shape of the lens. Circular lenses are easier to make, but square or rectangular pictures are more "sensible".

Because the photographic roll of film is that shape, and also the photo printing paper is, too

This is because the camera sensor that records what your taking is a rectangle. The sensor retains the correct aspect ratio. As for the lens being a circle, for one its a lot easier to twist a circle than it would be a square or rectangle to zoom. Follow this link, it has some great information on how cameras and lenses work

http://electronics.howstuffworks.com/cam...