JEE Mains · Physics · STD 12 - 9. Ray optics and optical instruments
The refractive index of a converging lens is \(1.4.\) What will be the focal length of this lens if it is placed in a medium of same refractive index ? (Assume the radii of curvature of the faces of lens are \(R _{1}\) and \(R _{2}\) respectively)
- A \(1\)
- B Infinite
- C \(\frac{ R _{1} R _{2}}{ R _{1}- R _{2}}\)
- D Zero
Answer & Solution
Correct Answer
(B) Infinite
Step-by-step Solution
Detailed explanation
\(\frac{1}{ F }=\left[\frac{\mu_{ L }}{\mu_{ S }}-1\right]\left[\frac{1}{ R _{1}}-\frac{1}{ R _{2}}\right]\) If \(\mu_{ L }=\mu_{ S } \Rightarrow \frac{1}{ F }=0 \Rightarrow F =\infty\)
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