WAEC - Physics (1992 - No. 27)
A real image of an object fom1ed by a converging lens of focal length 15cm is three times the size of the object. What is the distance of the object from the lens?
30cm
25cm
20cm
15cm
10cm
คำอธิบาย
1/u + 1/3u = 1/15; u = 20cm