NEET2015Physics-Optics
NEET 2015 Physics Lens Formula MCQ Question
Type: MCQ-numerical-Hard-Class 12
Two identical thin plano-convex glass lenses (refractive index 1.5) each having radius of curvature of 20 cm are placed with their convex surfaces in contact at the centre. The intervening space is filled with oil of refractive index 1.7. The focal length of the combination is
A
-20 cm
B
25 cm
C
-50 cm
D
50 cm
Correct Answer
Option B
Detailed Explanation
Using the lens maker's formula and considering the combination of lenses and oil, the effective focal length can be calculated.
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