Question

a student is unable to see clearly the word written on the blackboard placed at a distance of approximately 3 m from him name the defect of vision the boy suffering from state the possible cause of this defect and explain the method of collecting it

Answer 1

The defect is myopia
Causes :
1) excessive curvature of eye lens
2)elongation of eye ball

Concave lens of suitable power is used for correction. It brings back image on retina by diverging the rays initially..

Answer 2

Myopia .
It can be caused by high converging power ( short focal length ) , long eye ball
It can be corrected by using a concave lens .
Concave Len is a diverging lens , so it diverge the light rays which enters the eye and make it to fall on the retina.