Two lenses of power -15D and +15D are in contact each other.the focal lengthof the combination is.\na)+20cm\nb)-10cm\nc)-20cm\nd)+20cm
shriyanshee , 10 Years ago
Grade
2 Answers
Saurabh Koranglekar
Last Activity: 4 Years ago
Dear students, Power of combination of lens is P1 + P2=2D + (-1.5 D) = 0.5 D
As power is positive lens is convex lens of power 0.5 D First Lens Power = +2.D Focal length = 1m /P = 100 cm/2 = 50 cm
focall length = 100 cm/1.5 = -67 cm
Vikas TU
Last Activity: 4 Years ago
Dear students, Power of combination of lens is P1 + P2=2D + (-1.5 D) = 0.5 D
As power is positive lens is convex lens of power 0.5 D First Lens Power = +2.D Focal length = 1m /P = 100 cm/2 = 50 cm It is a convex lens Ascend lens Power = -1.5 focall length = 100 cm/1.5 = -67 cm Itr is a concave lens with negative focal length. Regards
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