The ratio of the speed of the electrons in the ground state of hydrogen to the speed of  light in vacuum is

  • A

    $1 / 2$

  • B

    $2 / 137$

  • C

    $1 / 137$

  • D

    $1 / 237$

Similar Questions

Hydrogen atom is excited from ground state to another state with principal quantum number equal to $4$. Then the number of spectral lines in the emission spectra will be

Match List $- I$ (Experiment performed) with List $-II$ (Phenomena discovered/associated) and select the correct option from the options given the lists

List $- I$ List $- II$
$(1)$ Davisson and Genner $(i)$ Wave nature of electrons
$(2)$ Millikan's oil drop experiment $(ii)$ Charge of an electron
$(3)$ Rutherford experiment $(iii)$ Quantisation of energy levels
$(4)$ Franck-Hertz experiment $(iv)$ Existence of nucleus

  • [JEE MAIN 2014]

Discuss the experimental results of Geiger-Marsden's $\alpha $ -particle scattering. 

Apply Bohr’s atomic model to a lithium atom. Assuming that its two $K$-shell electrons are too close to nucleus such that nucleus and $K$-shell electron act as a nucleus of effective positive charge equivalent to electron. The ionization energy of its outermost electron is......$eV$

An electron having de-Broglie wavelength $\lambda$ is incident on a target in a X-ray tube. Cut-off wavelength of emitted $X$-ray is :