Question

A person is nearsighted with a far point of 75.0 cm. a. What focal length contact lens is needed to give him normal vision

Answer 1

Complete Question

The  complete question is  shown on the first uploaded image  

Answer:

a

  $f= -75 \ cm = - 0.75 \ m$

b

  $P = -1.33 \ diopters$

Explanation:

From the question we are told that

    The  image distance is  $d_i = -75 cm$

The value of the image is negative because it is on the same side with the corrective glasses

    The  object distance is  $d_o = \infty$

The  reason object distance  is because the object father than it being picture by the eye

General focal length is mathematically represented as

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

substituting values

             $\frac{1}{f} = \frac{1}{-75} - \frac{1}{\infty}$

=>         $f= -75 \ cm = - 0.75 \ m$

Generally the power of the corrective lens is  mathematically represented as

        $P = \frac{1}{f}$

substituting values

       $P = \frac{1}{-0.75}$

        $P = -1.33 \ diopters$