If the focal length of the lens used in aerial photography is 50mm, what should be the distance from the film to the lens? Why? Please elaborate. Thank you! (physics)

This should be a physics problem in high school.

According to the formula of object distance u, image distance v and focal length f

1/u+ 1/v= 1/f

It can be concluded that

1/v= 1/f- 1/u

v=uf/(u-f)=(u/(u-f))f

Because u is large, u/(u-f) is slightly larger than 1.

It can be seen that the image distance should be slightly greater than 50mm, and the answer is A.

The distance from the film to the lens is the image distance.