Which of the following equations gives the angular momentum of an electron in a stationary orbit?

When an electron with energy $10.8 \,eV$ collides with a hydrogen $(H)$ atom,what will happen?

On what factors does the magnitude of the velocity of an electron in an orbit depend?

Positronium consists of an electron and a positron (a particle which has the same mass as an electron,but opposite charge) orbiting round their common centre of mass. Calculate the value of the Rydberg constant for this system.

What is the work function of the metal if the light of wavelength $4000 \, \mathring{A}$ generates photoelectrons of velocity $6 \times 10^5 \, ms^{-1}$ from it? ............. $eV$ (Mass of electron $= 9 \times 10^{-31} \, kg$; Velocity of light $= 3 \times 10^8 \, ms^{-1}$; Planck's constant $= 6.626 \times 10^{-34} \, Js$; Charge of electron $= 1.6 \times 10^{-19} \, C \, eV^{-1}$)

If the potential energy of an electron in a hydrogen atom is $-3.02 \ eV$,then the electron is present in which of the following excited states?