If a convex lens of focal length 12cm is used to produce a real image four times the size of the object, how far from the lens must the object be placed?
-
A.
10 cm -
B.
15 cm -
C.
20 cm -
D.
25 cm
Correct Answer: Option B
Explanation
Magnifications = V/U = 4
∴ V = 4U1/V + 1/U = 1/f1/4u + 1/U = 1/125/4U = 1/12
4U = 12 x 5 = 60
∴ U = 15 cm