Optics (Physics) Part-III

Convex lenses are used in magnifying devices due to their magnifying properties. A convex lens has the capacity to make an object appear much larger than it actually is.

Hence, it is used in the magnifying glass. Magnifying glass is used to enlarge items such as writing so it can be read more easily.

Far-sightedness (hypermetropia) as it is medically termed is a vision condition in which distant object are usually seen clear, but near objects are not clearly visible. To remove this vision problem one should use a convex lens.

Far-sightedness (hypermetropia) is a common vision problem, affecting about a fourth of the population. People with hypermetropia can see distant objects very well but have difficulty in focusing on objects that are close.

This vision problem occurs when light rays entering the eye focused behind the retina rather than directly on it. The eyeball of a farsighted person is shorter than normal. A convex lens is used to correct this defect.

A convex lens is thicker in the middle and thinner at the edges. Rays of light that pass through the lens are brought closer together. A convex lens is also called a converging lens. A convex lens is used in reading glasses and it also used to remove the defect of far-sightedness.

A concave lens is used to minimize the defect of myopia.

Myopia or near-sightedness is a refractive error which means that the eye does not bend or refract light properly to a single focus to see the image clearly. In Myopia, close objects look clear but distant objects appear blurred. It is corrected by using a concave lens.

Myopia or near-sightedness is a refractive error which means that the eye does not bend or refract light properly to a single focus to see the image clearly. In Myopia, close objects look clear but distant objects appear blurred. It is corrected by using a concave lens.

Myopia or near-sightedness is a refractive error which means that the eye does not bend or refract light properly to a single focus to see the image clearly. In Myopia, close objects look clear but distant objects appear blurred. It is corrected by using a concave lens.

Myopia (near-sightedness) and Hypermetropia (far-sightedness) can be respectively corrected by concave and convex lens.

The amount of light entering the eye through pupil is controlled by iris. But this adjustment takes some time; for example, our eyes cannot see everything clearly when we enter a darkroom from a bright light because in bright light, the size of pupil of our eye is small.

When we enter the dark room, due to small size of pupil, very little light enters our eyes. But after some time, the pupil expands which permits more light to enter into eyes and we become able to see things.

So the option (a) is correct. Also it takes some time for the eyes to adapt with darkness and the reason behind this are rods & cones. These are two types of cells in our retina that absorb light. The rods help us to see in the dark while cones help us to see under bright conditions.

So, when a person moves from a well lit area to a dark from a well lit area to a dark area, initially he's not able to see clearly because cones cease functioning in low light.

Also, the rod pigments (rhodopsins) have been bleached out due to the bright light and these cells cannot function normally again until the bleach pigments are restored back to their unbleached state and this takes time. Hence, option (c) and (d) are also correct for this question.