Physics

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You want to take a full length photo of your friend who is 2 m tall, using a 35 mm camera having a 50 mm lens. The image dimensions of 35 mm film is 24 mm by 36 mm, and you want to make this a vertical photo in which your friend's image completely fills the image area. (a) How far should your friend stand from the lens? (b) How far is the lens from the film?

• Physics -

(a) The magnification ratio 2.0/0.036 = 55.56, tells you the do/di ratio.
You also know that
1/do + 1/di = 1/0.050 m = 20 m^-1

Solve for do

1/do + 55.56/do = 56.56/do = 20
do = 2.83 m

di = 2.83/55.56 = 0.0509m = 50.9 mm

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