One lens of a nearsighted person's eyeglasses has a focal length of - 28.0 cm, and the lens is 1.8 cmfrom the eye. If the person switches to contact lenses that are placed directly on the eye, what should be the focal length of the corresponding contact lens?

focal length is - 29.8 cm

Explanation:

given data

focal length = - 28.0 cm

distance = 1.8 cm

to find out

focal length

solution

we apply here lens formula

1/f = 1/p + 1/q

here p is infinity and f = - 28 and

-1/28 = 0 + 1/q

q = - 28 cm

so

distance from eye = 28 cm + 1.8 cm = - 29.8 cm

so f will be

1/f = 1/p + 1/q

1/f = 1/infinity - 1/29.8

f = - 29.8

so focal length is - 29.8 cm