A contact lens is made of plastic with an index of refraction 2.70.The lens has an outer radius of curvature of + 3.3 cm and an inner radius of curvature of + 4.5 cm.What is its focal length?

Question

Quizplus · Accepted Answer

The focal length of a lens can be calculated using the lens maker's formula:

1/f = (n-1) * (1/R1 - 1/R2)

where n is the index of refraction of the lens, R1 is the radius of curvature of one surface, and R2 is the radius of curvature of the other surface.

Plugging in the given values, we get:

1/f = (2.70 - 1) * (1/0.033 - 1/0.045)
1/f = 1.70 * (30.3 - 22.2)
1/f = 1.70 * 8.1
1/f = 13.77
f = 1/13.77 = +0.0727 m = +7.3 cm

Therefore, the focal length of the contact lens is +7.3 cm, which is answer choice D.

A Contact Lens Is Made of Plastic with an Index