There is a small air bubble at the centre of a solid glass sphere of radius $r$ and refractive index $\mu$. What will be the apparent distance of the bubble from the centre of the sphere,when viewed from outside?

Monochromatic light of frequency $5 \times 10^{14} \ Hz$ travelling in vacuum enters a medium of refractive index $1.5$. Its wavelength in the medium is ....... $\mathring{A}$.

The distance travelled by light in glass (refractive index $= 1.5$) in a nanosecond will be.......$cm$.

The velocity of light in a medium is $1.5 \times 10^8 \ m/s$. Its refractive index will be:

$A$ tank is filled with water to a height of $12.5 \, cm$. The apparent depth of a needle lying at the bottom of the tank is measured by a microscope to be $9.4 \, cm$. If water is replaced by a liquid of refractive index $1.63$ up to the same height,what will be the apparent depth of the needle in $cm$?

In the figure given below,a ray of light travelling in a medium of refractive index $\mu$ passes through two different connected rectangular blocks of refractive indices $\mu_1$ and $\mu_2$ $(\mu_2 > \mu_1)$. The angle of incidence $\theta_1$ is increased slightly. Then,the angle $\theta_2$ is