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Explain how you can take care of your eyes

A social worker was addressing people at an eye donation camp organised in a colony. He said that there are millions of blind people in our country who cannot see at all. The eyesight of most of these blind people can be restored if we donate our eyes by making a pledge in writing to the eye bank that, after our death, our eyes should be removed and given to the blind people. He said, in this way we can pass on the priceless gift of vision to our blind brothers and sisters to light up their dark world, without losing anything. By listening to the social worker, many people (including some students) filled up the pledge forms to donate their eyes, after death. (a) Whitin how much time of the death of person, his donated eyes must be removed and preserved so as to remain good for transplantation ? (b) What happens to those donated eyes which are not good for transplanation ? (c) Can a person having AIDS disease donate eyes ? (d) Can a person having diabetes disease donate eyes ? (e) How many blind people can get eyesight if ten persons their eyes ? (f) What values of social worker are exhibited by his address ?

(a) Draw a diagram to show the formation of image of a distant object by a myopic eye. How can such an eye defect be remedied ? (b) State two reasons due to which this eye defect may be caused. ( c) A person with myopic eye cannot see objects beyond a distance of 1.5 m . What would be the power of the corrective lens used to restore proper vision ?

a) The anlge subtended at the eye by an object is equal to the angle subtended at the eye by the virtual image produced by a magnifying glass. In what sense then does a magnifying glass provide angular magnifications? b) In viewing through a magnifying glass, one usually positions one's eyes very close to the lens. Does angular magnification change if the eye is moved back? c) Magnifying power of a simple microscopes is inversely proportional to the focal length of the lens. What then stops us from using a convex lens of smaller and smaller focal length and achieving greater and greater magnifying power? d) Why must both the objective and the eyepiece of a compound microscope have short focal lengths? e) When viewing through a compound microscope, our eyes should be positioned not on the eyepiece but a short distance away from it fot best veiwing. Why? How much should be that short distance between the eye and eyepiece?

A 60 W bulb is placed at a distance of 4 m from you. The bulb is emtting light of wavelength 600 nm uniformly in all directions. In 0.1 s, how many photons enter your eye if the pupil of the eye is having a diameter of 2mm? [take hc=1240eV-nm]

(a) What is short-sightedness ? State the two causes of short-sightedness (or myopia). With the help of ray diagram, show : (i) the eye-defect short-sightedness. (ii) correction of short-sightedness by using a lens. (b) A person having short-sight cannot see objects clearly beyond a distance of 1.5 m. What would be the nature and power of the corrective lens to restore proper vision ?