JEE Mains · Physics · STD 12 - 9. Ray optics and optical instruments
Two identical thin biconvex lenses of focal length \(15\, cm\) and refractive index \(1.5\) are in contact with each other. The space between the lenses is filled with a liquid of refractive index \(1.25\). The focal length of the combination is \(cm\).
- A \(10\)
- B \(101\)
- C \(18\)
- D \(11\)
Answer & Solution
Correct Answer
(A) \(10\)
Step-by-step Solution
Detailed explanation
\(\frac{1}{ f _{1}}=\frac{1}{15}=\left(\frac{3}{2}-1\right)\left[\frac{2}{ R }\right]\) \(\frac{1}{ R }=\frac{1}{15}\) \(\frac{1}{ f _{\text {eq }}}=\frac{1}{ f _{1}}+\frac{1}{ f _{2}}+\frac{1}{ f _{3}}\)…
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