Focal length of lens is 0.75 m, what will be its refreactive power -
The most convenient system for ophthalmic purpose is the one which takes a lens with focal distance of 1 meter as standard. Such a lens has a power of 1 dioptre (D). Thus , simple formula to calculate the refreactive power of a lens is - 1 Refractive power (D)= -------------------------------- Focal length (meter) 1 In this question refractive power =---------------------=1.33D 0.75 Reference : Parson&;s 22nd edition page 47
0.75D
1.5D
1.25 D
1.33 D
Optics and refraction