Calculate the distance of closest approach to the nucleus of z = 80 when a 8MeV electron incident on it reverses its direction.

Two insulated charged metallic spheres A and B have their centres separated by a distance of 50 cm in air (1) calculate the force of répulsion between them, if the charge on each is +5.0xx 10 ^(-8) C (ii ) calculate the force of repulsion between them when the two spheres are placed in water. (dielectric constant of water is 81.0)

In Bohr's model of hydrogen atom, the electron circulats around nucleus on a path of radius 0.53A^@ at a frequency of 6.8 xx 10^15 rev//sec . Calculate magnetic field induction at the centre of the nucleus. What is the effective magnetic dipole moment?