Question

Noopur needs a lens of power -4.5 for correction of her vision. what kind of defect in vision is she suffering from. what is the focal length of the corrective lens. draw ray diagrams showing the defected eye and correction for this defect. What are the causes of this defect

Answer 1

P=-4.5D
 since the power of the lens is negative, it is a concave lens.
So the defect from which Noopur is suffering from is Myopia.
f=1/P
f=1/-4.5
f=-0.2222m
f=-22.22m
the defect is myopia and it is caused by
a) increase in the curvature of the lens or decrease in focal length of eye lens
b) elongation of eye ball.
(Sorry I could"t down load the images but you can refer the NCERT book for the diagrams)

Answer 2

Explanation:

since the sign is- it is concave which indicated the condition is myopia.

the focal length is 22.2 by the formula f=1 by f