Electrostatic force between two identical charges placed in vacuum at distance of $$r$$ is F. A slab of width $$\frac{r}{5}$$ and dielectric constant 9 is inserted between these two charges, then the force between the charges is
A ray is incident from a medium of refractive index 2 into a medium of refractive index 1. The critical angle is
An electric dipole with dipole moment $$5 \times 10^{-7} \mathrm{C}-\mathrm{m}$$ is in the electric field of $$2 \times 10^4 \mathrm{NC}^{-1}$$ at an angle of $$60^{\circ}$$ with the direction of the electric field. The torque acting on the dipole is
A capacitor of capacitance $$C_1=1 \mu \mathrm{F}$$ is charged using a 9 V battery. $$C_1$$ is, then removed from the battery and connected to capacitors $$C_2$$ and $$C_3$$ of $$2 \mu \mathrm{F}$$ and $$3 \mu \mathrm{F}$$, respectively as shown in the figure. Find the charge on $$C_3$$ after equilibrium has reached is