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Question
Two convex lens of focal length 0.2 m and one concave lens of focal length 0.1 m is kept, as shown below. What is the effective power of the combination of the lens?
Two convex lens of focal length 0.2 m and one concave lens of focal length 0.1 m is kept, as shown below. What is the effective power of the combination of the lens?
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Solution
The correct option is B 0 Dioptre
Given,
Focal length of two convex lens = 0.2 m
Focal length of the concave lens = -0.1
Effective power of a combination of lens is given by:
P = P1 + P2 + P3
Also
Power (P) = 1/Focal length(m)
P1 = 1 / (0.2 m)= 5 D
P2 =1/(-0.1 m) = -10 D
P3 =1/( 0.2 m) = 5 D
Hence effective power (P) =5 - 10 + 5 = 0 D
Given,
Focal length of two convex lens = 0.2 m
Focal length of the concave lens = -0.1
Effective power of a combination of lens is given by:
P = P1 + P2 + P3
Also
Power (P) = 1/Focal length(m)
P1 = 1 / (0.2 m)= 5 D
P2 =1/(-0.1 m) = -10 D
P3 =1/( 0.2 m) = 5 D
Hence effective power (P) =5 - 10 + 5 = 0 D
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