Camera Lens – Optics Level 4

In this problem, we have a converging lens
of focal length, f0. We wish to find the range of movement of lens needed such that any object
at a distance greater than x from the film is focused onto it. We can consider the two
limiting cases in order to solve this problem. When the object is placed at infinity, u=infinity
and the photographic film is placed at a distance Vmin from the lens. By using the lens equation,
and the fact that 1/u goes to zero as u goes to infinity, we can find Vmin. The other case
to be considered is when the lens is at a distance Vmax from the film. The object a
distance u from the lens and the object a distance x from the photographic film. We
know that u + Vmax=x. Therefore using the lens equation, we can find Vmax and thus the
range of movement needed to answer the question.

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