A converging lens produces an image four times as large a...
A converging lens produces an image four times as large as an object placed 25cm from the lens. Calculate its focal length
100cm
33cm
29cm
20cm
Correct answer is D
M = vu
v = mu = 4 x 25 = 100m
1v+1u=1f
1100+125=1f
f = 20cm