Optics part (3)

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 and hypermetropia 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.

We see the world around us because of the way our eyes bend (refract) light. The refractive or bending power of the cornea and humor is constant. However, that of the lens can be changed by changing its shape. That is by making it more or less convex so that light can be properly focused on the retina. The greater the lens convexity or bulge the more it bends the light. The flatter the lens, the less it bends that light.

The eye lens is composed of a fibrous, jelly-like material. Its curvature can be modified to some extent by the ciliary muscles. The change in the curvature of the eye lens can thus change its focal length. When the muscles are relaxed, the lens becomes thin. Thus its focal length increases. This enables us to see distant objects clearly. When you are looking at objects closer to the eye, the ciliary muscles contract. This increases the curvature of the eye lens. The eye lens then becomes thicker. Consequently, the focal length of the eye lens decreases. This enables us to see nearby objects clearly.

Head Mirror is mostly used by doctors for the examination of ear, nose, and throat. It comprises a circular concave mirror, with a small hole in the middle and is attached to a head-band. Hence statement (d) is not correct. Remaining statements are correct.

The normal eye can focus a sharp image of an object on the eye if the object located anywhere from the infinity to a certain point called near point the minimum distance of an object from the eye to have its clear image is called least distance vision it is about 25 cm for the normal eye and donated by D.

The normal eye can focus a sharp image of an object on the eye if the object located anywhere from the infinity to a certain point called near point the minimum distance of an object from the eye to have its clear image is called least distance vision it is about 25 cm for the normal eye and donated by D.