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Step 2First find the focal length of your lens
You'll need a light source, a measuring tape, the lens and a screen, for right now a piece of paper makes an adequate screen.
Lay the tape out on a flat surface and place the screen at the zero point. Then place the lens at 2N on the tape (with N being any reasonable number to start, say 2 inches) and the light source at 4N. Now slowly move the lens and the light source away from the screen, while keeping the distance ratio the same, until the light source is in focus on the screen. At this point the lens focal length is equal to N.
I assume this is a valid approach since 1/u+1/v=1/f The basic simple lens calculation. Sorry no image, but you can do this empirically as well.
Lay the tape out on a flat surface and place the screen at the zero point. Then place the lens at 2N on the tape (with N being any reasonable number to start, say 2 inches) and the light source at 4N. Now slowly move the lens and the light source away from the screen, while keeping the distance ratio the same, until the light source is in focus on the screen. At this point the lens focal length is equal to N.
I assume this is a valid approach since 1/u+1/v=1/f The basic simple lens calculation. Sorry no image, but you can do this empirically as well.
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