Multiple choice

Focussing in a camera is carried out by varying ______.

  1. the amount of light

  2. distance of the lens from the screen

  3. distance of the lens from the object

  4. the speed of the shutter
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

In a camera, focusing adjusts the lens-to-sensor distance to satisfy the lens equation 1/f = 1/u + 1/v. The lens must be positioned so that the image forms precisely on the sensor/film. Moving the lens changes the image distance to achieve sharp focus at different object distances.

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