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?

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

so by lens formula we have

so we have

f = -3.5 m

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

The voltage across the element is = 240 V

I hope you understand....

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