Question

If a nearsighted person has a far point dfdfd_f that is 3.50 mm from the eye, what is the focal length f1f1f_1 of the contact lenses that the person would need to see an object at infinity clearly?

Answer 1

Answer:

person must have to use the concave lens of focal length 3.5 m

Explanation:

If the person can see upto distance of 3.5 m from eye

then in order to see the object at large distance we need to use

$d_o = infinite$

$d_i = -3.5 m$

so by lens formula we have

$\frac{1}{d_i} + \frac{1}{d_o} = \frac{1}{f}$

$\frac{1}{-3.5} + 0 = \frac{1}{f}$

so we have

f = -3.5 m

so person must have to use the concave lens of focal length 3.5 m