Question

sushil went to an eye specialist for check up.He prescribed him to use spectacle lens of +0.5 power (a) Name the defect of vision he is suffering from (B) find the focal lenght of spectacle lens?

Answer 1

Answer:

he is suffering from myopia

focal length:1/f

1/0.5

2metres

Answer 2

Given:

• Sushil went for eye-checkup. Doctor prescribed him +0.5 D lens.

To find:

• What optical defect is he suffering from?
• Focal length of lens ?

Calculation:

• First of all, the lens prescribed to Sushil is a CONVEX LENS (as evident from positive power).

• Convex lens are used to see nearby objects when the person can't see near objects.

• So, Sushil is suffering from HYPERMETROPIA.

Now, focal length will be :

$P = \dfrac{1}{f \: (in \: metres)}$

$\implies \: + 0.5 = \dfrac{1}{f}$

$\implies \: f = \dfrac{1}{0.5}$

$\implies \: f = 2 \: metres$

So, focal length of lens is 2 metres