The wavelength of the first line of Balmer series of hydrogen atom is $\lambda \,\mathop A\limits^o $. The wavelength of this line of a double ionised lithium atom $(Z = 3)$is
$\lambda /3$
$\lambda /9$
$\lambda /8$
$\lambda /27$
An $X-$ ray tube is operated at $50\, kV$. the minimum wavelength produced is.......$\mathop A\limits^o $
The ratio of speed of an electron in ground state in Bohrs first orbit of hydrogen atom to velocity of light in air is
Which of the following statements are true regarding Bohr's model of hydrogen atom
$(I)$ Orbiting speed of electron decreases as it shifts to discrete orbits away from the nucleus
$(II)$ Radii of allowed orbits of electron are proportional to the principal quantum number
$(III)$ Frequency with which electrons orbits around the nucleus in discrete orbits is inversely proportional to the principal quantum number
$(IV)$ Binding force with which the electron is bound to the nucleus increases as it shifts to outer orbitsSelect correct answer using the codes given belowCodes :
Why atoms are electrical neutral ?
In a hydrogen atom, the electron is in $n^{th}$ excited state. It may come down to second excited state by emitting ten different wavelengths. What is the value of $n$ :