A person cannot read newspaper placed nearer than 50 cm from his eyes. Name the defect of vision he is suffering from. Draw a ray diagram to illustrate this defect. List its two possible causes. Draw a ray diagram to show how this defect may be corrected using a lens of appropriate focal length.

A person cannot read newspaper placed nearer than 50 cm from his eyes.

1.	A person cannot read newspaper placed nearer than 50 cm from his eyes. Name the defect of vision he is suffering from. Draw a ray diagram to illustrate this defect. List its two possible causes. Draw a ray diagram to show how this defect may be corrected using a lens of appropriate focal length.
Answer» <P> Solution :(a) The person is suffering from hypermetropia. Two possible CAUSES : (i) Greater focal length of the lens. (ii) Eye ball becoming smaller. Use CONVEX lens of focal length `u=-25cm` `v=-50cm`. `(1)/(f)=(1)/(v)-(1)/(u)=(1)/(-50)-(1)/(-25)` `=(-1+2)/(50)=(1)/(50)cm rArr f=50cm` `P=(100)/(50)="2 D is required 1"`