Question

A woman can see clearly with her right eye only when objects are between 45 cm and 155 cm away. Prescription bifocals should have what powers so that she can see distant objects clearly (upper part) and be able to read a book 25 cm away (lower part) with her right eye? Assume that the glasses will be 2.0 cm from the eye.

Answer 1

Answer:

Explanation:

given,

A woman can see object between 45 cm and 155 cm

glasses is 2 cm from the eye

to able to read a book distance = 25 cm

For the  object distant apart

$\dfrac{1}{f}= \dfrac{1}{p} +\dfrac{1}{q}$

$\dfrac{1}{f}= \dfrac{1}{\infty}+\dfrac{1}{-153}$

$\dfrac{1}{f} = - 6.53 \times 10^{-3}$

hence, D = - 0.653  m

For the object at the near point

$\dfrac{1}{f}= \dfrac{1}{p} +\dfrac{1}{q}$

$\dfrac{1}{f}= \dfrac{1}{23} +\dfrac{1}{-43}$

$\dfrac{1}{f}= 0.0202 cm$

hence, D = 2.02 m