If a concave 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
Verified Correct Answer: B.
Physical Principles & Numerical Solution
Magnifications = V/U = 4
∴ V = 4U
1/V + 1/U = 1/f
1/4u + 1/U = 1/12
5/4U = 1/12
4U = 12 x 5 = 60
∴ U = 15 cm
Source: WAEC / JAMB / NECO Classroom Archive (Record #14490)