2007-03-16 23:09:14 · 4 answers · asked by ouma06 1 in Science & Mathematics ➔ Physics
The optical power of a lens with a focal length of 1 meter (about 39 inches) is said to be 1 diopter. Because the formula is based on the reciprocal of the focal length, a 2 diopter lens is not 2 meters but 1/2 meter, a 3 diopter lens is 1/3 meter and so forth. This is important because magnification increases as the focal length gets shorter, which is why a prescription for a higher diopter correction means you need more magnification.
A diopter is the reciprocal of the focal length of lens expressed in meters.
Focal length is measured in diopters
2007-03-16 23:23:07 · answer #1 · answered by J.SWAMY I ఇ జ స్వామి 7 · 0⤊ 0⤋
See the links.
2007-03-16 23:24:30 · answer #2 · answered by Kes 7 · 0⤊ 0⤋
with a ruler!!
the actual distance can be measured many ways expeimentaly
most common is to get parallel light from distant object (houses through window) and (by moving a screen back and forward, or static screen moving lens) find where a sharp image of 'houses' is formed. the distance between the mid point of lens and the screen is ur focal length
2007-03-16 23:23:09 · answer #3 · answered by pat_arab 3 · 0⤊ 0⤋
From the surface of the lens to the exposure plate. Anyway, that's how the math works on a "soft camera" in 3D programming. So, I assume the math approximates the real world for this question.
2007-03-16 23:17:45 · answer #4 · answered by Anonymous · 0⤊ 0⤋