A Contact Lens Is Made of Plastic with an Index

Multiple Choice

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?

A) -7.3 cm
B) +4.6 cm
C) +1.1 cm
D) +7.3 cm
E) -1.1 cm