what is meant by power of a lens ? what does its sign (positive or negative) indicate ? State its S.I unit . How is this unit related to focal length of a length in centimeters ?
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The converging or diverging ability of a lens is called power of lens..... Power is defined as the reciprocal of focal length of lens.
P=1/f (in m)
P=100/f (in cm)
For convex lens f=+
For concave f =-
S.I unit is dioptre = D
P=1/f (in m)
P=100/f (in cm)
For convex lens f=+
For concave f =-
S.I unit is dioptre = D
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