The work function of a metal $M$ is $6.3 \ eV$. The wavelength of the incident radiation required to just eject the electrons from its surface (in $nm$) is

Calculate the wavelength for the emission transition if it starts from the orbit having radius $1.3225 \, nm$ and ends at $211.6 \, pm$. Name the series to which this transition belongs and the region of the spectrum.

$A$ metal surface is exposed to $500 \ nm$ radiation. The threshold frequency of the metal for photoelectric current is $4.3 \times 10^{14} \ Hz$. The velocity of the ejected electron is $....... \times 10^{5} \ ms^{-1}$ (Nearest integer).
[Use : $h=6.63 \times 10^{-34} \ Js, m_{e}=9.0 \times 10^{-31} \ kg$]

Consider one $He^{+}$ ion is in excited state $(n = 5)$. Which of the following observations hold true as per the Bohr's model?

What is the ratio of the radii of the second orbit for $H$,$He^{+}$,and $Li^{2+}$?

The Ritz combination principle states that: