If the magnification of a virtual image formed of an object 10cm from a convex lens is 3, then the focal length of the lens is
A
10cm
B
15cm
C
16cm
D
19cm
E
20cm
Verified Correct Answer: B.
Physical Principles & Numerical Solution
V = 3u, U = 10cm
therefore U = -ve,
F = \(\frac{UV}{U + V}\)
= \(\frac{10 \times (-30)}{10 - 30 }\)
= 15cm
Source: Myschool Past Questions Archive (Record #29094)