CBSE Class 8 Answered

Hi Minku, A lens having both surfaces bulging outwards is called a double convex lens or simply a convex lens. A convex lens is thicker at the middle than at the edges. The convex lens converges the light rays incident on it to a point. Hence, a convex lens is also known as a converging lens. A lens having both surfaces curved inwards is called a double concave lens or simply a concave lens. A concave lens is thicker at the edges than at the middle. The concave lens diverges the light rays incident on it. Hence, a concave lens is also known as a diverging lens.