013 (part 1 of 2) 10.0 points A nature photographer is using a camera that has a

Question

013 (part 1 of 2) 10.0 points

A nature photographer is using a camera that has a lens with a focal length of 2.81 cm. The photographer is taking pictures of ancient trees in a forest and wants the lens to be focused on a very old tree that is 17.7 m away.

How far must the lens be from the film in order for the resulting picture to be clearly focused?

Answer in units of cm.

014 (part 2 of 2) 10.0 points

How much would the lens have to be moved to take a picture of another tree that is only 2.72 m away?

Answer in units of cm.

Explanation / Answer

A.

f = 2.81 cm = 0.0281 m

u = 17.7 m

1/u + 1/v = 1/f

1/v = 1/f - 1/u

v = fu/(u - f)

v = 0.0281*17.7/(17.7 - 0.0281)

v = 0.028144 m = 2.8144 cm

B.

u = 2.72 m

v = fu/(u - f)

v = 0.0281*2.72/(2.72 - 0.0281) = 0.0283 m

v = 2.83 cm

dv = 2.83 - 2.8144 = 0.0156 cm

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