A convex lens of focal length 25 cm and a concave lens of focal length 10 cm are placed in close contact with each other. Calculate the lens power of this combination.
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Concave lens
f = 25 cm = 25/100m
P = -1/25/100 D
= - 100/25D
= - 4 D..................(1)
Convex lens
f = 10 cm = 100/10m
P = 1/10/100 D
= 100/10
= 10 D .................(2)
Power of both the lens when they are kept in contact = power of convex lens + power of concave lens
= 10 +(-4)D
= 6D
f = 25 cm = 25/100m
P = -1/25/100 D
= - 100/25D
= - 4 D..................(1)
Convex lens
f = 10 cm = 100/10m
P = 1/10/100 D
= 100/10
= 10 D .................(2)
Power of both the lens when they are kept in contact = power of convex lens + power of concave lens
= 10 +(-4)D
= 6D
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