A student is not able to see clearly the questions written in the black board placed at a distance of 2.5 m from him:
(i) Name the defect of vision he is suffering from?
(ii) Draw a diagram to show the defect?
(iii) Name the type of lens used to correct this effect?
(iv) Name two possible causes of this effect?
(v) Draw a diagram to show how this defect can be corrected
Answers
(Points 2 and 5 have been drawn below)
(i) The defect of vision he is suffering from is called Myopia.
(iii) This type of defect can be corrected by using Concave lens.
(iv) The two possible causes of Myopia are:-
(a) Increase in the length of the eyeball
(b) Distance of retina from the eye lens has increased
(c) Decrease in focal length of the eye lens when the eye is fully relaxed or suffering from tension
(i) The student is suffering from the defect of vision named Myopia or short-sightedness.
Average distance a human eye can see is 6 meters. The blackboard is 2.5 m from the student, so, the student is unable to see object that are distant. Thus, this condition is called myopia or short-sightedness.
(ii) The image is attached below.
(iii) The type of lens used is concave lens.
This lens converges the light from the object to make the distant objects visible.
(iv) The two possible causes are age and continuous work with laptop.
The eyeball gets elongated which reduces the focal length of the eye ball. This results in diversion of light ray from the surface of retina.
(v) The image is attached below.
