Question

Complete the following sentence:
(i) A short sighted person cannot see ______ object clearly. Short sightedness can be correct by using _____ lenses.
(ii) A long sighted person cannot see ______ object clearly. Long sighted can be corrected by using ______ lenses.

Answer 1

Hint: - The short sight is often called nearsightedness or myopic. And the long sight is used to call distant sightedness or hypermetropia. As the name suggests they are rectified using convex or concave mirrors.

Complete Step by step solution:
 (i) In short sighted people the light coming from the distant objects is focused at a point in front of the retina. This occurs when the eyeball is too long or when the cornea is too curved. Thus the lens is not able to focus the image from the distant objects on the retina. But the near objects are visible clearly. The image of near objects is easily focused on the retina. Hence the short sight is called nearsightedness. This short sight or myopia is corrected using the concave lens. By using the concave lens in front of the eyes the light will bend and converge to focus the image on the retina.
Thus a short sighted person cannot see distant objects clearly. Short sightedness can be correct by using concave lenses.
(ii) In a long sighted person the light coming from the near objects is focused at a point behind the retina. Thus the lens is not able to focus the image from the near objects on the retina. But the distant objects are visible clearly. The image of distant objects is easily focused on the retina. Hence the long sight is called distant sightedness. This long sight or hypermetropia is corrected using the convex lens.
Thus a short sighted person cannot see near an object clearly. Long sightedness can be correct by using convex lenses.

Note: The concave lens is also called minus lens. In short sight the image is said to be over focused. Thus it is rectified by a concave lens. In long sight the image is not over focused since the image is formed behind the retina.