Question

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

a) What kind of defect in vision is she suffering from?

b) What is the focal length and nature of the corrective lens?

c) Draw ray diagrams showing the (a) defected eye and (b) correction for this

defect.

d) What are the causes of this defect?

Answer 1

Hi there!

P= -4.5diopter

a) The person is suffering from Myopia where he can see near distance clearly but finds difficulty in seeing distant objects.

b) We know that P=1/f

P = - 1/4.5

=-0.222m

=-22.2cm
[Negative sign indicates it is concave lens.]

c) Please refer the attachment.

d) Causes are :

• Elongated eye ball
• Greater focal length.

Cheers!

Answer 2

a) she is suffering from myopia
b) p=100/f cm
-4.5=100/f cm
F= 100/-4.5 = -22.2
It is a concave lens
D) eye ball being long
Or
Converging power of lens being high