concave lens of focal length 20 cm is placed its contact with a concave lens of focal length 30 cm calculate the focal length of the lens combination what is its power ??
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concave lens of focal length 20 cm is placed its contact with a concave lens of focal length 30 cm calculate the focal length of the lens combination what is its power ??
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Answer:
focal of convex lens(f)=+20cm=20/100=+.20 m
P=1/f=1/.20=100/20=+5D
focal length of concave lens(f)=-10cm=-10/100=-.1 m
P=1/-.1=-10D
power of combination=5-10=-5D