Question

When you focus a camera, you adjust the distance of the lens from the film. If the camera lens acts like a thin lens, why can it not be a fixed distance from the film for both near and distant objects?

a. A fixed distance would cause chromatic aberration.
b. A fixed distance would violate the thin lens formula.
c. A fixed distance would result in spherical aberration.
d. A fixed distance would not account for variations in object distance.

Answer 1

The lens distance from the film cannot be fixed for both near and distant objects due to variations in object distance, violating the thin lens formula. Focusing a camera involves adjusting the lens-to-film distance to ensure a clear image on the film or image sensor.

Step-by-step explanation:

When focusing a camera, you adjust the distance of the lens from the film. If the camera lens acts like a thin lens, it cannot be a fixed distance from the film for both near and distant objects due to variations in object distance. The thin lens formula, which relates the object distance, image distance, and focal length of a lens, would be violated if the lens-to-film distance is fixed. In order to focus on near objects, the lens needs to be moved farther away from the film, and for distant objects, it needs to be moved closer to the film.

Focusing a camera involves adjusting the lens-to-film distance to ensure that the image falls precisely on the film or image sensor to produce a clear image. The ciliary muscles of the eye also adjust the shape of the eye lens for focusing on nearby or far objects, changing the focal length of the lens. This mechanism of the eye is called accommodation.