lens

A lens is a curved, transparent piece of glass or plastic that bends light to form a larger, smaller, or clearer image of an object.

• A lens works because light changes direction when it passes from air into glass (and back out again). This bending of light is called refraction.
• Many lenses are thicker in the middle and thinner at the edges. Such a lens is a convex lens, and it can make nearby small objects look magnified (bigger).
• When you hold a magnifying glass over a page, the lens makes the letters look larger because it makes the light rays spread out in a way that your eye sees a bigger image.
• Not every lens makes things look bigger. A lens that is thinner in the middle and thicker at the edges (a concave lens) usually makes things look smaller and is used in some spectacles.
• Lenses are important because they are the main parts of tools like microscopes, telescopes, and even the human eye, helping us see things more clearly or see objects too small or far away for our eyes alone.