Diverging lens
A concave lens is otherwise known as a diverging lens.
A convex lens is also known as a converging lens, while a concave lens is also known as a diverging lens.
Concave and convex can refer the types of lenses used to treat refractive errors in the eyes. Concave is another word for myopic lens and convex is another name for a hyperopic lens also known as nearsighted and farsighted respectively
A diverging lens, also known as a concave lens, always forms virtual images. This type of lens diverges incoming light rays, causing them to appear to originate from a point behind the lens, resulting in the formation of a virtual image.
A converging lens is also known as a convex lens.
There is no other name for the objective lens. However, the eyepiece is also called the ocular lens.
Another name is eyepiece or eyepiece lens.
If light is incident of a convex lens, light will meet at the focal point, on the other side of the lens. In case of concave lens, light will be diverged. Convex and concave lens are very important in study of optics.
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Bifocals.
The eye lens may become too thick & its focal length is reduced. the ciliary muscles are not able to relax sufficiently to make the eye lens thin when viewing distant objects. So, they are unable to increase the focal length of the lens & the image is formed before retina. Since short sightedness occurs due to excessive convergence of light rays by the eye lens, it can be corrected by using a diverging lens, i.e, a concave lens. A properly chosen focal length of a concave lens compensates the extra convergence of the eye lens thus, removing the defect. The scientific name of short sightedness is myopia.