Two lenses of power 6 D and – 2 D are combined to form a single lens. The focal length of this lens will be
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Answer:
Focal length of combination= 0.25m
= 25 cm
Explanation :
Power of first lens ( P1) = 6 D
Power of second lens (P2) = - 2 D
Power of combination of lenses =
= P1 + P2
= 6 D + (-2D)
= 6 D - 2 D
= 4 D
We know that,
Power ( P) = 1/focal length(f) { in metres}
P = 1/f
f = 1/ P
f = 1/ 4
f = 0.25 metres = 25 centimeter
Hence, focal length of the combination of lenses = 0.25 m
= 25 cm
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