Which one of the following alternatives is $FALSE$ for a prism placed in a position of minimum deviation?

$A$ thin prism $P_1$ with an angle $6^{\circ}$ and made of glass of refractive index $1.54$ is combined with another prism $P_2$ made from glass of refractive index $1.72$ to produce dispersion without average deviation. The angle of prism $P_2$ is $........{}^{\circ}$

$A$ ray of light incident on one face of an equilateral glass prism having refractive index $\sqrt{2}$, produces the emergent ray which just grazes along the adjacent face. The value of angle of incidence is $(\sin 90^{\circ} = 1, \sin 30^{\circ} = 0.5, \sin 45^{\circ} = 1/\sqrt{2})$.

The prism angle of a prism is $40^{\circ}$. $A$ light ray is incident at $38^{\circ}$ and undergoes minimum deviation. The angle of minimum deviation is ........$^{\circ}$.

$A$ prism having refractive index $\sqrt{2}$ and refracting angle $30^{\circ}$ has one of the refracting surfaces silvered. The beam of light incident on the other refracting surface will retrace its path,if the angle of incidence is $\left[\sin \frac{\pi}{6}=0.5\right]$

The angle of minimum deviation produced by a thin prism in air is $\delta_1$. If it is immersed in water,the angle of minimum deviation is $\left[_{a}\mu_{g}=\frac{3}{2}, _{a}\mu_{w}=\frac{4}{3}\right]$.