Which of the following has the lowest melting point?

$A$ positively charged $(+q)$ particle of mass $m$ has kinetic energy $K$ and enters a region with a horizontal magnetic field of induction $\vec{B}$ in a vertically downward direction. The acceleration of the particle is:

Which process is used for the removal of hardness of water?

If $(2, -1, 3)$ is the foot of the perpendicular drawn from the origin to a plane, then the equation of that plane is

In a metre bridge experiment,the ratio of the left gap resistance to the right gap resistance is $2:3$. The balance point from the left is: (in $~cm$)

$A$ ray of light strikes a plane mirror $M$ at an angle of $45^o$ as shown in the figure. After reflection,the ray passes through a prism of refractive index $1.5$ whose apex angle is $4^o$. The total angle through which the ray is deviated is......$^o$