What is the focal length of a pair of contact lenses that will allow a person with a near point of 125.0 cm to read a newspaper held 25.0 cm from his eyes?
A) -100 cm
B) -31.3 cm
C) 10.2 cm
D) 20.8 cm
E) 31.3 cm

Question

Quizplus · Accepted Answer

The focal length of the contact lenses is given by the equation:1/f = 1/do + 1/diwhere do is the object distance (25.0 cm) and di is the image distance (125.0 cm). Substituting these values into the equation, we get:1/f = 1/25.0 cm + 1/125.0 cm1/f = 0.04 cm^-1 + 0.008 cm^-11/f = 0.048 cm^-1f = 20.8 cmTherefore, the focal length of the contact lenses is 20.8 cm.

What Is the Focal Length of a Pair of Contact