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Which lens has greater power, the lens with greater focal length or smaller focal length?
1 Answer
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- Anonymous5 years ago
Smaller focal length = greater power
A small focal length means the lens has to bend the light more to get the light focussed near the lens.
Power (measured in dioptres, D) is related to focal length (in metres, m).
P = 1/f and f = 1/P
E.g.
a focal length of 50cm (=0.5m) is a power of 1/0.5 = 2D
a focal length of 20cm (=0.2m) is a power of 1/0.2 = 5D
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