A person needs a lens of power, – 5.5 dioptres for correcting his distant vision. For correcting
A person needs a lens of power, – 5.5 dioptres for correcting his distant vision. For correcting his near vision, he needs a lens of power, +1.5 dioptres. What is the focal length of the lens required for correcting
1. distant vision
2. near vision ?
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1. For distant vision:
P = -5.5D
P = 1/f
f = 1/P = 1/(-5.5)
= -0.1818 m = -18.18cm
2. For Near Vision:
P = 1.5D P = 1/f
f = 1/P = 1/1.5 = 0.6666 = 66.66 cm
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