Question

100 pts.
An object 8.25 cm from a lens creates a virtual image at -26.8 cm from the lens. What is the focal length of the lens?

(Mind your minus signs.) (Unit = cm)

Answer 1

Answer:

1 / f = 1 / i + 1 / o             1 / f = (o + i) / i o

f = i o / (o + i)

f = -26.5 * 8.25 / (8.25 - 26.8)

f = -221 / -.308 = 11.8 cm