a) A person is to be fitted with bifocals. She can see clearly when the object i

Question

a) A person is to be fitted with bifocals. She can see clearly when the object is between 26.0cm and 1.6m from the eye. Since the upper portion of the bifocals should be designed to enable her to see distant objects clearly, what is the power they should have (in diopters)? (Assume there is no significant distance between the eye and the glasses lens.) Remember that distant objects should be focused on the far point. Make sure to give the right sign. Submit Answer Incorrect. Tries 5/10 Previous Tries

b) The lower portion of the bifocals in the question above should enable her to see objects comfortably at 25.0cm. What power should they have (in diopters)

Explanation / Answer

(a)
Far point = 1.6 m
1/f = 1/di + 1/do
p = - 1/1.6 + 1/
p = - 0.625 diopters.

(b)
Now in this case, the image should be formed at his near point.
1/f = 1/di + 1/do
p = -1/0.26 + 1/0.25
p =  0.154 diopter.

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