In the given figure potential at point 'A' is 900 volt and point 'B' is earthed. What will be the potential at point 'P' ?

Kinetic energy of a proton is equal to energy '$$E$$' of a photon. Let '$$\lambda_1$$' be the de-Broglie wavelength of proton and '$$\lambda_2$$' is the wavelength of photon. If $$\frac{\lambda_1}{\lambda_2} \alpha E^n$$, then the value of '$$n$$' is

A drop of liquid of density '$$\rho$$' is floating half immersed in a liquid of density '$$d$$'. If '$$T$$' is the surface tension, then the diameter of the drop of the liquid is

Assuming the atom is in the ground state, the expression for the magnetic field at a point nucleus in hydrogen atom due to circular motion of electron is [$$\mu_0=$$ permeability of free space, $$\mathrm{m}=$$ mass of electron, $$\epsilon_0=$$ permittivity of free space, $$\mathrm{h}=$$ Planck's constant ]