Four alkali metals $A$,$B$,$C$ and $D$ have standard electrode potentials $-3.05 \ V$,$-1.66 \ V$,$-0.40 \ V$ and $0.80 \ V$ respectively. Which metal will be the most reactive?

Emulsification of $10 \, mL$ of oil in water produces $24 \times 10^{18}$ droplets. If the surface tension at the oil-water interface is $0.03 \, J \, m^{-2}$ and the area of each droplet is $12.5 \times 10^{-16} \, m^2$,the energy spent in the formation of oil droplets is $.... \, J$.

Which of the following pairs of orbitals possess two nodal planes?

The magnifying power of a telescope is $9$. When it is adjusted for parallel rays,the distance between the objective and eyepiece is $20 \ cm$. The focal lengths of the lenses are:

If $200 \text{ MeV}$ of energy is released in the fission of one nucleus of ${ }_{92}^{235} \text{U}$,then the number of nuclei that must undergo fission to release an energy of $1000 \text{ J}$ is

The figure shows the cross-sectional view of a hollow cylindrical conductor with inner radius $R$ and outer radius $2R$. The cylinder carries a uniformly distributed current $i$ along its axis. The magnetic induction at point $P$ at a distance $\frac{3R}{2}$ from the axis of the cylinder will be: