$A$ ray of light passes through an equilateral prism $(\mu = 1.5)$ such that the angle of incidence is equal to the angle of emergence,and the latter is equal to $3/4$ of the prism angle. The angle of deviation is....$^o$

Four convergent lenses have focal lengths $100 \, cm, 10 \, cm, 4 \, cm$ and $0.3 \, cm$. For a telescope with maximum possible magnification,we choose the lenses of focal lengths:

There are two coils $A$ and $B$ as shown in the figure. No current flows in $B$ if $A$ is at rest. Now,the coil $A$ is made to rotate about a vertical axis. At the shown instant $(t = 0)$,what will be the direction of the current in coil $A$ if the induced current in coil $B$ is counterclockwise?

$A$ tank with vertical walls is mounted so that its base is at a height $H$ above the horizontal ground. The tank is filled with water to a depth $h$. $A$ hole is punched in the side wall of the tank at a depth $x$ below the water surface. To have maximum range of the emerging stream,the value of $x$ is

If $z = \sec(y - ax) + \tan(y + ax)$,then $\frac{\partial^2 z}{\partial x^2} - a^2 \frac{\partial^2 z}{\partial y^2}$ is equal to

Which metal does not react with cold water but releases $H_2$ gas upon reacting with steam?