+956 A lens has a focal length of +20.0 cm, and a magnification of –4.00. What is the distance between the object and the image?
+37146 A coupe of physics equations:
1/f = 1/do + 1/di do = object distance di = image distance
and M = -di/do or do = -di/M (substitute into the first equation)
1/20 = 1/(-di/-4) + 1/di
1/20 = 4/di + 1/di
1/20 = 5/di di = 5(20) = 100 cm
M= -di/do
-4 = -100/do do = 25 cm
Distance between do and di = 100 + 25 = 125 cm
