Question 93: Ray Optics

Question

A concave-convex lens of refractive index 1.5 and the radii of curvature of its surfaces are 30 cm and 20 cm, respectively. The concave surface is upwards and is filled with a liquid of refractive index 1.3. The focal length of the liquid-glass combination will be

Accepted Answer

$$\begin{aligned}
\frac{1}{\mathrm{f}} & =\left(\frac{1.3-1}{1}ight)\left(\frac{1}{\infty}-\frac{1}{-30}ight) \
& =\left(\frac{1.5-1}{1}ight)\left(\frac{1}{-30}-\frac{1}{-30}ight) \
& =\frac{0.3}{30}+\frac{0.5}{60}=\frac{1}{100}+\frac{1}{120} \
& =\frac{6+5}{600}=\frac{11}{600} \
\mathrm{f} & =\frac{600}{11} \mathrm{~cm}
\end{aligned}$$

Answer

$ \frac{700}{11} $ cm

Answer

$ \frac{600}{11} $ cm

Answer

$ \frac{800}{11} $ cm

Answer

$ \frac{500}{11} $ cm

Ray Optics

A concave-convex lens of refractive index 1.5 and the radii of curvature of its surfaces are 30 cm and 20 cm, respectively. The concave surface is upwards and is filled with a liquid of refractive index 1.3. The focal length of the liquid-glass combination will be

Choose the correct answer: