Physicshard · Past Paper
Which of the following describes the 'f-number' of a camera?
AFocal length / Aperture diameter
BAperture diameter / Focal length
CFocal length * Aperture
D1 / Focal length
✓ Correct Answer: A — Focal length / Aperture diameter
The f-number (focal ratio) is the ratio of the lens's focal length to the diameter of the entrance pupil.
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