For a camera to work, it needs two things: a light-sensitive surface to capture an image, and a lens that bends the light from a given scene and projects it onto the light-sensitive surface. The earliest known cameras, known as camera obscura, did not use lenses and employed just a hole in a wall, but the results were not that good. For truly great pictures, you need lenses, and the most important type of lens present in cameras is the convex lens.
How Lenses Work
A lens is essentially a transparent object made of glass, plastic or other material that bends light through a process called refraction. Because it possess the characteristics of a wave, light essentially changes speed and direction whenever it passes from one environment to another; in this case, from gaseous air to solid glass or plastic. The light passing through a lens bends twice, once as it enters the glass or plastic and again as it leaves, according to the book “How Everything Works.”