Leaching of $Ag_2S$ is carried out by heating it with a dilute solution of

For an ellipse with eccentricity $e = \frac{1}{2}$,the centre is at the origin. If one directrix is $x = 4$,then the equation of the ellipse is:

Two metal wires of identical dimensions are connected in series. If $\sigma_{1}$ and $\sigma_{2}$ are the electrical conductivities of the metal wires respectively, the effective conductivity of the combination is

In the circuit shown,a meter bridge is in its balanced state. The meter bridge wire has a resistance of $0.1 \ \Omega/cm$. Find the value of the unknown resistance $X$ and the current drawn from the battery of negligible internal resistance.

If we use pyrene $(CCl_4)$ in the Riemer-Tiemann reaction in place of chloroform,the product formed is

Consider the following statements $A$ and $B$. Identify the correct choice in the given answers.
$A$. The refractive index of the extra-ordinary ray depends on the angle of incidence in double refraction.
$B$. The vibrations of light waves acquire one-sidedness for both ordinary and extraordinary rays in double refraction.