In the figure shown,$\frac{\sin i}{\sin r}$ is equal to:

In refraction,light waves are bent on passing from one medium to the second medium,because,in the second medium

When light is refracted from air into glass,

If light passes near a massive object,the gravitational interaction causes a bending of the ray. This can be thought of as happening due to a change in the effective refractive index of the medium given by $n = 1 + \frac{2GM}{rc^2}$,where $r$ is the distance of the point of consideration from the centre of the mass of the massive body,$G$ is the universal gravitational constant,$M$ is the mass of the body,and $c$ is the speed of light in vacuum. Considering a spherical object,find the deviation of the ray from the original path as it grazes the object.

$A$ fish rising vertically at the rate of $3 \, m/s$ to the surface of water observes a bird above the water,diving vertically towards it at the rate of $9 \, m/s$. The refractive index of water is $4/3$. Calculate the actual velocity (velocity $w.r.t$ ground) of the bird in $m/s$.

$A$ monochromatic beam of light is travelling from medium $A$ of refractive index $n_{1}$ to a medium $B$ of refractive index $n_{2}$. In the medium $A$,there are $x$ number of waves in a certain distance. In the medium $B$,there are $y$ number of waves in the same distance. Then,the refractive index of medium $A$ with respect to medium $B$ is