i. Name the defect of eye from which she is suffering. ii. What type of lens is she using? iii. Find the focal length of the lens.

Question

Sunita from Std. X uses spectacles. Her spectacle number is -1.5 D.

i. Name the defect of eye from which she is suffering.

ii. What type of lens is she using?

iii. Find the focal length of the lens.

Answer 1

i. Myopia.

ii. Concave.

iii. \(P=\frac{1}{f}\)

(Concave lens ∴ minus sign) 

This is the focal length of the lens.