Question 83: Ray Optics

Question

A biconvex lens of refractive index 1.5 has a focal length of $$20 \mathrm{~cm}$$ in air. Its focal length when immersed in a liquid of refractive index 1.6 will be:

Accepted Answer

$$\begin{aligned}
& \mu_1=1.5 \
& \mu_m=1.6 \
& f_a=20 \mathrm{~cm} \
& 	ext { As } \frac{f_m}{f_a}=\frac{\left(\mu_1-1ight) \mu_m}{\left(\mu_1-\mu_might)} \
& \frac{f_m}{20}=\frac{(1.5-1) 1.6}{(1.5-1.6)} \
& f_m=-160 \mathrm{~cm}
\end{aligned}$$

Answer

$$-$$16 cm

Answer

+16 cm

Answer

+160 cm

Answer

$$-$$160 cm

Ray Optics

A biconvex lens of refractive index 1.5 has a focal length of $20 \mathrm{~cm}$ in air. Its focal length when immersed in a liquid of refractive index 1.6 will be:

Choose the correct answer: