posted by Blegh .
A 5.00 cm tall candle is placed at a distance of 50.0 cm from a double convex lens having a focal length of 15.0 cm. What is the magnification of the image?
(1/p) + (1/q) = 1/f
M = h'/h = -q/p,
Where p is distance of object from lens, q is distance of image from lens, f is focal length of the lens, and M is the magnification
f is positive when the lens is convex:
1/50 + 1/q = 1/15
q = 21.4 cm
M = -21.4/50