Define concave lens, convex lens, optical density and refraction

Answer 1

Concave lens: A concave lens is a type of lens that is thinner at the center and thicker at the edges. It causes light rays to spread out, or diverge, thereby creating smaller and virtual images. Concave lenses are used to treat myopia or nearsightedness.

Convex lens: A convex lens is a lens that is thicker at the center and thinner at the edges. It converges light rays and forms larger and real images. Convex lenses are commonly used in cameras, telescopes, and eyeglasses to correct hyperopia or farsightedness.

Optical density: Optical density refers to the measure of how much a material or medium can slow down the speed of light passing through it. It is usually represented by the refractive index of the material. The higher the optical density, the more the material can bend or refract light.

Refraction: Refraction is the bending or change in direction of light as it passes from one medium to another medium of different optical density. When light travels from a less dense to a more dense medium, such as from air to water, it bends towards the normal line (the perpendicular line to the interface). Conversely, when it travels from a more dense medium to a less dense medium, such as from water to air, it bends away from the normal line. Refraction is responsible for various optical phenomena, including the formation of rainbows and the way lenses focus light.