A camera lens used for taking close-up photographs has a focal length of 23.0 mm. The farthest it can be placed from the film is 34.0 mm. (a) What is the closest object (in mm) that can be photographed

The object distance is 71.09 mm.                              

Explanation:

A camera lens used for taking close-up photographs has a focal length of 23.0 mm, f = 23 mm

The farthest it can be placed from the film is 34.0 mm, v = -34 cm

Using lens formula as follow :

So, object distance is 71.09 mm.

the duration of a photographic flash is related to an rc time constant, which is 0.100 μs for a certain camera.