NEET2019Physics-Optics
NEET 2019 Physics Lens Combination MCQ Question
Type: MCQ-conceptual-Hard-Class 12
Two similar thin equiconvex lenses, of focal length f each, are kept coaxially in contact with each other such that the focal length of the combination is F. When the space between the two lenses is filled with glycerin (which has the same refractive index (μ = 1.5) as that of glass) then the equivalent focal length is F₂. The ratio F₁ : F₂ will be:
A
2 : 3
B
3 : 4
C
2 : 1
D
1 : 2
Correct Answer
Option D
Detailed Explanation
When the space is filled with a medium of the same refractive index, the lenses effectively behave as a single lens with double the focal length. Thus, F₁ : F₂ = 1 : 2.
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