Question

The lens of a healthy human eye can focus onto the retina light coming from objects lying in a range of distances from 0.10 m to infinity. It does so by contracting a set of muscles that compress the lens, thereby changing its focal length. The distance between the retina and the lens is 17 mm. What is the range of focal lengths that the eye lens can attain

Answer 1

Step-by-step explanation:

In the given case , distance between lens and retina = 17 mm

image distance v = 17 mm

object distance u = .1 m = - 100 mm

from lens formula

1 / v - 1 / u = 1 / f

1 / 17 - 1 / 100 = 1 / f

f = 20.48 mm

For object at infinity

u = infinity , v = 17 mm

from lens formula

1 / v - 1 / u = 1 / f

1 / 17 - 1 / ∞ = 1 / f

1 / 17 = 1 / f

f = 17 mm

So range of focal lengths that the eye lens can attain

is 17 mm to 20.48 mm .