A photographer uses a camera lens with focal length of 50.0 mm to photograph a tree that is 4.60 m tall. She wishes to fill her 24.0-mm slide with the tree.
(a) How far from the lens should the film be?
(b) What is the magnification of the image?
A couple of physics equations (again )
M= hi / ho = - di / do (1) and f = 1/do + 1/di (2)
M = 24 mm / 4600 mm = .005217 = magnification
also using (1) di =- hi/ho * do = - .005217 do (we'll substitute this in to (2) )
1/50 = 1/do + 1/di Substitiute for di
1/50 = 1/do + 1 /(-.005217do)
1/50 = 1/do - 191.666/do = distance from object to lens
do = - 9533.33 mm (negative means object side of the lens) = 9.533 m from the lens
(Hope I did the calcs correctly! )