Question

Aniket from standard 10 uses spectacles the power of the lens in his spectacles is - 0.5 D answer the following question a )state the type of lenses used in spectacles b )name the defect of vision Aniket is suffering from c)
find the focal length of the lens is used in spectacles

Answer 1

a) Concave lens
b) Myopia
c) P = 1/F (in m)
-0.5D = 1/F
F= -1/0.5
F= -2 m
F = 200cm

Answer 2

Answer: (a) The concave lens is used in the spectacles.

(b) The defect vision is myopia.

(c) The focal length of the lens is - 2cm.

Explanation:

In the given problem, Aniket from standard 10 uses spectacles the power of the lens in his spectacles is - 0.5 D.

(a) The power of the spectacles is negative. The concave lens is used in the spectacles. Aniket is suffering from myopia. Myopia can be corrected by concave lens.

(b) The person suffering from myopia can see nearby object clearly but he cannot see distant object. Aniket is suffering from myopia.

(c)

The formula for power is as follows;

$P=\frac{1}{f}$

Here, f is the focal length.

Calculate the focal length.

$f=\frac{1}{P}$

Put P=- 0.5 D.

$f=\frac{1}{-0.5}$

$f=- 2$

Therefore, the focal length of the lens is - 2cm.