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Two lenses of power -15 ~D and +5 ~D are in contact with each other. The focal length of the combination is

Options

  1. A-20 ~cm
  2. B-10 ~cm
  3. C+20 ~cm
  4. D+10 ~cm

Correct answer

B. -10 ~cm

Step-by-step solution

aligned & P=P₁+P₂=-10 & f= 1 P -0.1 ~m -10 ~cm aligned

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