JEE Mains · Physics · STD 12 - 9. Ray optics and optical instruments
A point object in air is in front of the curved surface of a plano-convex lens. The radius of curvature of the curved surface is \(30 \;\mathrm{cm}\) and the refractive index of the lens material is \(1.5 .\) then the focal length of the lens (in \(\mathrm{cm}\) ) is
- A \(58\)
- B \(62\)
- C \(60\)
- D \(67\)
Answer & Solution
Correct Answer
(C) \(60\)
Step-by-step Solution
Detailed explanation
Using Lens-Maker's formula \(\frac{1}{f}=(\mu-1)\left(\frac{1}{R_{1}}-\frac{1}{R_{2}}\right)\) \(\Rightarrow \frac{1}{f}=(1.5-1)\left(\frac{1}{30}-0\right)\) \(\mathrm{f}=60 \mathrm{cm}\)
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