Noopur needs a lens of power -4.5D for correction of her vision

Noopur needs a lens of power -4.5D for correction of her vision.

  1. What kind of defect in vision is she suffering from?
  2. What is the focal length and nature of the corrective lens?
  3. Draw ray diagrams showing the (a) defected eye and (b) correction for this defect.
  4. What are the causes of this defect?

Answer

a) Myopia

b) f = -1/4.5 = 0.22 cm

Concave lens

c)

d) Causes:

i) Due to excess curvature of eye lens
ii) Elongation of the eye ball