Work required to pull an electron from helium atom is 40 eV. Then the work required to pull both the electrons from the helium atom is

For ionizing an excited hydrogen atom, the energy required (in $eV$) will be

An ionic atom equivalent to hydrogen atom has wavelength equal to ${\rm{1/4}}$ of the wavelength of hydrogen lines. The ion will be

Orbital acceleration of electron is

In a sample of hydrogen like atoms all of which are in ground state, a photon beam containing photons of various energies is passed. In absorption spectrum, five dark lines, are observed. The number of bright lines in the emission spectrum will be (assume that all transitions takes place)

In a spectrum of hydrogen atom, the ratio of shortest wavelength in Lyman series to longest wavelength in Paschen series is

The wavelength of Lyman series is

Maximum wavelength in Balmer series of hydrogen spectrum is (R : Rydberg constant)

Imagine an atom made up of a proton and a hypothetical particle of double the mass of the electron but having the same charge as the electron. Apply the Bohr’s atom model and consider all possible transitions of this hypothetical particle to the first excited level. The longest wavelength photon that will be emitted has wavelength $\lambda$ (given in terms of the Rydberg constant $R$ for the hydrogen atom) is equal to

In an atom for the electron to revolve around the nucleus, the necessary centripetal force is obtained from the following force exerted by the nucleus on the electron

For production of characteristic ${K_\beta }\;X$-rays, the electron transition is