Q21 of 25 Page 11

An old man cannot see objects closer than 1 m from the eye clearly. Name the defect of vision he is suffering from. How can it be corrected? Draw ray diagram for the (i) defect of vision and also(ii) for its correction. ( CBSE 2009)

The person cannot see nearby objects and is able to see far objects clearly, so he is suffering from Myopia also called near sightedness also his least point of distinct vision is far than that of normal eye. To correct this type of defect concave lens or diverging lens are needed because image is formed in front of retina rather than on retina.

i. The ray diagram for the defect of vision of the eye is



The image is formed in front of retina.


ii. The ray diagram for correction of defect of vision is



By correction, the image is formed on the retina, for correction we use concave lens or diverging lens.

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The far point of a myopic person is 80 cm in front of the eye. What is the nature and power of the lens required to correct the problem? ( CBSE 2006)

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State the cause of dispersion of white light passing through a glass prism. How did Newton show that white light of Sun contains seven colors using two identical glass prisms. Draw a ray diagram to show the path of light when two identical glass prisms are arranged together in inverted position with respect to .each other and a narrow beam of white light is allowed to fall obliquely on one of .the focus of the first prism. ( CBSE 2017, 2016, 2012, 2008)

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A student suffering from myopia is not able to see distinctly the objects placed beyond 5 m. List two possible reasons due to which this defect of vision may have arisen. With the help of ray diagrams, explain(i) why the student is unable to see distinctly the objects placed beyond 5 m from his eyes.(ii) the type of the corrective lens used to restore proper vision and how this defect is corrected by the use of this lens. ( CBSE 2017)