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The object distance, image distance, and focal length are related by Inspecting

ID: 1588866 • Letter: T

Question

The object distance, image distance, and focal length are related by Inspecting this expression, we see that for a fixed focal length, as the object distance gets smaller the image distance must get in order to maintain the equality. Due to the construction of the camera, there is a limit to how big the image distance can be and still get a sharp image on the detector. In order to allow smaller object distance (which is the case for a close-up shot), the photographer can use a focal length lens.

Explanation / Answer

Thin lens equation is given by -
1/object distance + 1/image distance = 1/focal length
Therefore Correct Option -
1/s' + 1/s = 1/f

Larger (This is quite evident from the formula, if we Decrease s , we need to increase s' for fixed focal length)

Smaller (The shorter the focal length, the wider the angle of view and the lower the magnification which is good for close up shot.)