A 50.0 mm lens is used to take a picture of an object 1.30 m tall located 4.00 m away. What is the height of the image on the film?
A) 21.0 mm
B) 16.5 mm
C) 12.0 mm
D) 10.5 mm
E) 9.20 mm

Question

Quizplus · Accepted Answer

Using the thin lens equation (1/f = 1/o + 1/i), where f is the focal length, o is the object distance, and i is the image distance, we can calculate the image distance:
1/f = 1/o + 1/i
1/0.050m = 1/4.00m + 1/i
i = 0.052m
The magnification of the image is given by m = -i/o, where the negative sign indicates that the image is inverted:
m = -i/o = -(0.052m)/(1.30m) = -0.04
The height of the image can be found using the magnification equation, h_i = |m|h_o, where h_o is the height of the object:
h_i = |m|h_o = (0.04)(1.30m) = 0.052m = 16.5 mm
Therefore, the height of the image on the film is 16.5 mm, which corresponds to choice (B).

A 500 Mm Lens Is Used to Take a Picture of of an Object