Question

You are designing eye glasses got someone whose neR point is 100 cm.

A) neglecting the eye lens distance, what focal length lens should you prescribe so that an object can clearly be seen when placed at 25 cm in front of the eye? (Hint =25 cm and q= -100 cm)

B) what is the lens power in diopters?

Answer 1

apply for diverging lens -1/f = 1/u + 1/v

u = object distance, = 25 cm

v= image distance = -100 cm

and f = focal length

magnifiication m = -(v/u) =y'/y ) =y'/y

f = uv/u+v

f = 25*-100/(25-100)

f = 33.34 cm is the focal length -------<<<<<<<<<<<<Answer

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Power P of a lens = 1/focal length in meter

Power P is measured in DIopters

so P = 1/0.3334

P = +3 Diopters ----------------------<<<<<<<<<<<<<<Answer

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