In this problem, you will determine the correct distance the imaging plane shoul

Question

In this problem, you will determine the correct distance the imaging plane should be from the lens for an object at a certain distance to be in focus. Assume the thin lens model discussed in lecture for a camera with a focal length of 35mm. An object in the scene will be in focus when all the rays from the object that pass through the lens converge at the same point on the imaging plane.

What should be the distance from the lens to the imaging plane for an object that is :

a)1m from the camera?

b) 100m from the camera?

Explanation / Answer

The formula for thin lense

1/p + 1/q = 1/f

f - focal length of the lense

p - distance between the lense and the object

q - distance between the lense and the image.

So for

a) p = 1m = 1000 mm f= 35 mm

q = 1/(1/f-1/p) = (1/(1/35 - 1/1000))
    = (1/(0.028 - 0.001)
    = 1/0.027
    = 37.03 mm

b) p = 100m = 100000 mm f= 35 mm

q = 1/(1/f-1/p) = (1/(1/35 - 1/100000))
    = (1/(0.02857 - 0.00001)
    = 1/0.02856
    = 35.01 mm

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