What is power of a lens?? explain how the two types of lens helps in correcting vision.
Answers
what is power of a lens?
A lens is a transparent piece of glass or plastic with at least one curved surface. It gets its name from the Latin word for "lentil" (a type of pulse used in cooking), but don't let that confuse you. There's no real reason for this other than that the most common kind of lens (called a convex lens) looks very much like a lentil!
explain how the two types of lens helps in correct ing vision?
Convex lenses are used in eyeglasses for correcting farsightedness, where the distance between the eye's lens and retina is too short, as a result of which the focal point lies behind the retina. Eyeglasses with convex lenses increase refraction, and accordingly reduce the focal length.
Explanation:
If a lens has a shorter focal length it is said to be more powerful. The power of a lens is defined as the reciprocal of the focal length. Lens power is measured in dioptres (D). Diverging (concave ) lenses have negative focal lengths, so they also have negative power values.
The lens changes the focus, so images fall on the retina as they should. The eye of a person with myopia is longer than normal. ... A concave lens is used to correct myopia to help focus images on the retina (top right). Farsightedness, or hyperopia, occurs when objects are focused in back of the retina (bottom left).