The `6563 oversetcircA H_alpha`line emitted by hydrogen in a star is found to be red-shifted by `15 oversetcircA`. Estimate the speed with which the star is recedng from the Earth.

A mercury lamp is a convenient source for studying frequency dependence of photoelectric emission, since, it gives a number of spectral lines ranging from the UV to the red end of the visible spectrum. In our experiment with rubidium photo-cell, the following lines from a mercury source were used: lambda_1 = 3650 oversetcircA , lambda_2=4047 oversetcircA , lambda_3=4358 oversetcircA , lambda_4=5461 oversetcircA , lambda_5=6907 oversetcircA The stopping voltages respectively were measured to be V_0=1.28 V , V_0.95V , V_0=0.74V , V_0=0.16 , V_0=0V Determine the value of Planck's constant h.

Bohr's model of hydrogen atom In order to explain the stability of atom and its line spectra, Bohr gave a set of postulates: An electron in an atom revolves in certain circular orbit around the nucleus. These are the orbits for which mvr=(nh)/(2pi) In these allowed orbits, the electron does not radiate energy. When an electron jumps from higher energy level E_(n_2) to lower energy orbit E_(n_1) , radiation is emittd and frequency of emitted electron is given by v=(E_(n_2)-E_(n_1))/h . Further the radius of the n^(th) orbit of hydrogen atom is r=(n^2h^24piepsilon_0)/(4pi^2me^2) and energy of the n^(th) orbit is given by E_n=-13.6/n^2 eV . If 13.6 eV energy is required to ionise the hydrogen atom, then enegy required to remove an electron from n=2 is:

Bohr's model of hydrogen atom In order to explain the stability of atom and its line spectra, Bohr gave a set of postulates: An electron in an atom revolves in certain circular orbit around the nucleus. These are the orbits for which mvr=(nh)/(2pi) In these allowed orbits, the electron does not radiate energy. When an electron jumps from higher energy level E_(n_2) to lower energy orbit E_(n_1) , radiation is emittd and frequency of emitted electron is given by v=(E_(n_2)-E_(n_1))/h . Further the radius of the n^(th) orbit of hydrogen atom is r=(n^2h^24piepsilon_0)/(4pi^2me^2) and energy of the n^(th) orbit is given by E_n=-13.6/n^2 eV . When hydrogen atom is the first excited level, it radius is:,

Bohr's model of hydrogen atom In order to explain the stability of atom and its line spectra, Bohr gave a set of postulates: An electron in an atom revolves in certain circular orbit around the nucleus. These are the orbits for which mvr=(nh)/(2pi) In these allowed orbits, the electron does not radiate energy. When an electron jumps from higher energy level E_(n_2) to lower energy orbit E_(n_1) , radiation is emittd and frequency of emitted electron is given by v=(E_(n_2)-E_(n_1))/h . Further the radius of the n^(th) orbit of hydrogen atom is r=(n^2h^24piepsilon_0)/(4pi^2me^2) and energy of the n^(th) orbit is given by E_n=-13.6/n^2 eV . The angular momentum of the orbital electron is integarl multiple of

Bohr's model of hydrogen atom In order to explain the stability of atom and its line spectra, Bohr gave a set of postulates: An electron in an atom revolves in certain circular orbit around the nucleus. These are the orbits for which mvr=(nh)/(2pi) In these allowed orbits, the electron does not radiate energy. When an electron jumps from higher energy level E_(n_2) to lower energy orbit E_(n_1) , radiation is emittd and frequency of emitted electron is given by v=(E_(n_2)-E_(n_1))/h . Further the radius of the n^(th) orbit of hydrogen atom is r=(n^2h^24piepsilon_0)/(4pi^2me^2) and energy of the n^(th) orbit is given by E_n=-13.6/n^2 eV . What would happen, if the electron in an atom is stationary?

Bohr's model of hydrogen atom In order to explain the stability of atom and its line spectra, Bohr gave a set of postulates: An electron in an atom revolves in certain circular orbit around the nucleus. These are the orbits for which mvr=(nh)/(2pi) In these allowed orbits, the electron does not radiate energy. When an electron jumps from higher energy level E_(n_2) to lower energy orbit E_(n_1) , radiation is emittd and frequency of emitted electron is given by v=(E_(n_2)-E_(n_1))/h . Further the radius of the n^(th) orbit of hydrogen atom is r=(n^2h^24piepsilon_0)/(4pi^2me^2) and energy of the n^(th) orbit is given by E_n=-13.6/n^2 eV . The ground state energy of hydroen atom is -13.6 eV. The KE and PE of the electron in this state are