If the velocity of an electron in the $n^{th}$ orbit of a Bohr atom is $v$,what is the value of $n$?

The electron in a hydrogen atom undergoes a transition from higher orbits to an orbit of radius $476.1 \text{ pm}$. This transition corresponds to which of the following series?

Why does the spectrum of an atom contain many lines even if only one electron is excited?

As we move away from the nucleus,the energy of the electron

Which of the following provisions of the Bohr atomic model of hydrogen turned out to be false?

Threshold frequency,$v_0$ is the minimum frequency which a photon must possess to eject an electron from a metal. It is different for different metals. When a photon of frequency $1.0 \times 10^{15} \ s^{-1}$ was allowed to hit a metal surface,an electron having $1.988 \times 10^{-19} \ J$ of kinetic energy was emitted. Calculate the threshold frequency of this metal. Show that an electron will not be emitted if a photon with a wavelength equal to $600 \ nm$ hits the metal surface.