) Look at the following diagram. The lens of a normal eye has a focal point that

Question

) Look at the following diagram. The lens of a normal eye has a focal point that lies on the retina, so that images can form there.

However, if the lens is misshaped, then the focal point moves. To correct this, we use corrective glasses.

If a person has a lens with focal length f = 1.2cm, and a corrective lens is placed 2 cm in front of the eye, what focal length should the corrective lens be to focus the image of an object 500m (50,000cm) in front of the eye onto the retina (1.7cm behind the eye’s lens)?

8.(4 points) Look at the following diagram. The lens of a normal eye has a focal point that lies on the retina, so that images can form there Focal point of lens and cornea Object at ee However, if the lens is misshaped, then the focal point moves. To correct this, we use corrective glasses. Object (a) Nearsighied eye If a person has a lens with focal length f= 1.2cm, and a corrective lens is placed 2 cm in front of the eye, what focal length should the corrective lens be to focus the image of an object 500m (50,000cm) in front of the eye onto the retina (1.7cm behind the eye's lens)?

Explanation / Answer

As u>> v in magnitude,

here, effective focal length, feff = 1.7 cm

focal length of eye lens, f1= 1.2 cm

corrective lens required is concave lens

we have,

1/feff = 1/f1 - 1/f + d/f1f

or, 1/1.7= 1/1.2 - 1/f + 2/(1.2f)

or, ( 1/f) *0.67= -0.2451

or, focal length of corrective lens, f = - 2.73 cm

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