Question 32
Lenses and Optical InstrumentsAn image in a convex lens is upright and magnified 3 times. If the focal length of the lens is 15 cm, what is the object distance?
- A.16cm
- B.14cm
- C.10cm
- D.25cm
Show the answer and explanation
Answer: C (10cm)
Explanation
An upright image is virtual, so v = −3u. 1/u − 1/(3u) = 1/15 gives 2/(3u) = 1/15, so u = 10 cm.