The far poiA woman can read the large print in a newspaper only when it is at a

Question

The far poiA woman can read the large print in a newspaper only when it is at a distance of 67 cm or more from her eyes. (a) Is she nearsighted (myopic) or farsighted (hyperopic), and what kind of lens is used in her glasses to correct her eyesight? (b) What should be the refractive power (in diopters) of her glasses (worn 2.9 cm from the eyes), so she can read the newspaper at a distance of 29 cm from the eyes?nt of a nearsighted person is 4.7 m from her eyes, and she wears contacts that enable her to see distant objects clearly. A tree is 20.6 m away and 2.0 m high. (a) When she looks through the contacts at the tree, what is its image distance? (b) How high is the image formed by the contacts?

Explanation / Answer

1. here women can read at distance 67 cm or more and we know that

if a person can not see an object nearly at 25 cm then there is hyperopic

in this condition the mirror image make outside the ratina

so we can use convex lens

2. the power of a lens is capacity of change the direction of light wave

it depend on the focus length of light

so P = 1 / f

here 1 /f = 1/v - 1/u

= 1/0.67 + 1/0.29

= 4.94 m

so P = 4.94m Ans

now if u = -4.7m v = 0.67m

so 1/f = 1/0.67 + 1/4.7

= 1.705m

so P = 1.705m Ans

now u = -20.6m m =2m

as we know that m = - v / u

so v = -2 x -20.6

= 41.2m Ans

here the mirror image is large from object during the convex lens

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