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A concave-convex lens of refractive index 1.5 and the radii of curvature of its surfaces are 30 cm and 20 cm , respectively. The concave surface is upwards and is filled with a liquid of refractive index 1.3. The focal length of the liquid-glass combination will be

Options

  1. A500 11 ~cm
  2. B800 11 ~cm
  3. C700 11 ~cm
  4. D600 11 ~cm

Correct answer

D. 600 11 ~cm

Step-by-step solution

aligned 1 f & = ( 1.3-1 1 ) ( 1 - 1 -30 ) & = ( 1.5-1 1 ) ( 1 -30 - 1 -30 ) & = 0.3 30 + 0.5 60 = 1 100 + 1 120 & = 6+5 600 = 11 600 f & = 600 11 ~cm aligned

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