A lens in a camera has a focal length, which is important for focusing the camera. If an object is at a distance D from the lens that has a focus length F, then to be in focus the distance S between..

Question

the lens and the film should satisfy the equation

1 over S = 1 over F subtract 1 over D

Write the difference 1 over F subtract 1 over D as one term.

1 over F subtract 1 over D = blank

Answer 1

1/F - 1/D = D / (FD) - F / (FD) = (D - F) / (FD)