Defects of Vision and their Correction

Vision requires :

The defect of vision in which the image of nearby object is formed behind the retina is 1

(a) A student is unable to see clearly the words written on the black board placed at a distance of approximately 3 m from him. Name the defect of vision the boy is suffering from. State the possible causes of this defect and explain the method of correcting it.

(a) A student suffering from myopia is not able to see distinctly the objects placed beyond 5 m . 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 corrective lens used to restore proper vision and how this defect is corrected by the use of this lens. (b) If in this case, numerical value of focal length of corrective lens is 5 m , find the power of the lens as per the new cartesion sign convention.

A person looking at a net of crossed wires is able to see the vertical direction more distinctly than the horizontal wires. What is the defect due to? How is such defect of vision corrected?

When the power of eye lens increases, the defect of vision is produced. The defect is known as

A person cannot see distinctly the book placed nearer than 60 cm from his eyes. (i) Name the defect of vision the person is suffering from. (ii) List two possible causes of this defect. (iii) Draw a ray diagram to show this vision defect. (iv) How can this defect be corrected ? (v) Draw a ray diagram to show the correction of this defect.

Due to gradual weakening of ciliary muscles and diminishing flexibility of the eye lens, a certain defect of vision arises. Write the name of this defect. Name the type of lens required by such persons to improve the vision. Explain the structure and function of such a lens.

A person is unable to see objects distinctly placed within 50 cm from his eyes. (a) Name the defect of vision the person is suffering from and list its two possible causes. (b) Draw ray diagram to show the defect in the above case. (c) Mention the type of lens used by him for the correction of the defect and calculate its power. Assume that the near point for the normal eye is 25 cm. (d) Draw a labelled diagram for the correction of the defect in the above case.

Which of the following statement regarding defects in solids is/are correct?