$A$ ray of light travelling in air has wavelength $\lambda$,frequency $n$,velocity $v$,and intensity $I$. If this ray enters into water,then these parameters are $\lambda'$,$n'$,$v'$,and $I'$ respectively. Which relation is correct from the following?

$A$ light ray is incident on a medium of refractive index $\mu$. The angle of incidence is twice the angle of refraction. The angle of incidence is:

Electromagnetic waves emanating from a point $A$ (in air) are incident on a rectangular block of material $M$ and emerge from the other side as shown below. The angles $i$ and $r$ are angles of incidence and refraction when the wave travels from air to the medium. Such paths for the rays are possible,

When light is refracted from air into glass,

If $\hat{i}$ denotes a unit vector along the incident light ray,$\hat{r}$ a unit vector along the refracted ray into a medium of refractive index $\mu$,and $\hat{n}$ a unit vector normal to the boundary of the medium directed towards the incident medium,then the law of refraction is:

$A$ fish rising vertically up towards the surface of water with speed $3 \; ms^{-1}$ observes a bird diving vertically down towards it with speed $9 \; ms^{-1}$. The actual velocity of the bird is.......$ms^{-1}$ (Assume refractive index of water $\mu = 4/3$).