$\begin{aligned}
& \frac{1}{8}=\left(\frac{\mu_{\ell}}{\mu_{\mathrm{s}}}-1\right)\left[\frac{1}{\mathrm{R}_1}-\frac{1}{\mathrm{R}_2}\right] \
& \frac{1}{24}=(1.5-1)\left[\frac{2}{\mathrm{R}}\right] ...(i)\
& \frac{1}{\mathrm{f}^{\prime}}=\left(\frac{1.5}{1.33}-1\right)\left(\frac{2}{\mathrm{R}}\right) \
& \frac{1}{\mathrm{f}^{\prime}}=\left(\frac{1.5 \times 3}{4}-1\right) \frac{2}{\mathrm{R}}...(ii)
\end{aligned}(i)dividedby(ii)\begin{aligned}
& \frac{\mathrm{f}^{\prime}}{24}=4 \
& \mathrm{f}^{\prime}=96 \mathrm{~cm}
\end{aligned}$
A convex lens made of glass (refractive index =1.5 ) has focal length 24 cm in air. When it is totally immersed in water (refractive index =1.33 ),…
JEE Main 2025 — Physics Optics
2025mcqmedium
A convex lens made of glass (refractive index =1.5 ) has focal length 24 cm in air. When it is totally immersed in water (refractive index =1.33 ), its focal length changes to
Official previous-year question
Held on 29 Jan 2025 · Verified 6 Jul 2026.
Options
- A
24 cm
- B
96 cm
- C
48 cm
- D
72 cm
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