A 101 mm focallength lens is used to focus an image on the s

A 101 mm -focal-length lens is used to focus an image on the sensor of a camera. The maximum distance allowed between the lens and the sensor plane is 135 mm .

How far ahead of the sensor should the lens be if the object to be photographed is 11.0 m away?

How far ahead of the sensor should the lens be if the object to be photographed is 3.3 m away?

How far ahead of the sensor should the lens be if the object to be photographed is 1.2 m away?

What is the closest object this lens could photograph sharply?

Solution

a) 1/do + 1/di = 1/f

di = do f / (do - f) = (11 * 0.101) / (11 - 0.101)

= 0.102 m

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b) 3.3 m away

di = do f / (do - f) = (3.3 * 0.101) / (3.3 - 0.101)

= 0.104 m

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c) 1.2 m away

di = do f / (do - f) = (1.2 * 0.101) / (1.2 - 0.101)

= 0.110 m

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d) 1/d_omax + 1/d_imax = 1/f

d_omax = (0.135 * 0.101) / (0.135 - 0.101)

= 0.401 m