Two lenses of power $6$ D and $- 2$ D are combined to from a signal lens. The focal length of this lens will be

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Solution

Given : $P_{1} = 6 D$ $P_{2} = - 2 D$
Power of combined lens $P = P_{1} + P_{2} = 6 - 2 = 4 D$
Focal length $F = \frac{1}{P} = \frac{1}{4} = 0.25 m = 25 c m$

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Two lenses of power 6D and −2D are combined to from a signal lens. The focal length of this lens will be

Given : P1=6 D P2=−2DPower of combined lens P=P1+P2=6−2=4DFocal length F=1P=14=0.25 m=25 cm

Two lenses of power $6$ D and $- 2$ D are combined to from a signal lens. The focal length of this lens will be

Given : $P_{1} = 6 D$ $P_{2} = - 2 D$
Power of combined lens $P = P_{1} + P_{2} = 6 - 2 = 4 D$
Focal length $F = \frac{1}{P} = \frac{1}{4} = 0.25 m = 25 c m$