If the first ionization energy of $H$ atom is $13.6 \ eV,$ then the second ionization energy of $He$ atom is (in $eV$)

The value of Planck's constant is $6.63 \times 10^{-34} \, J \cdot s$ and the speed of light is $3.0 \times 10^8 \, m \cdot s^{-1}$. The wavelength of a quantum of light with a frequency of $8 \times 10^{15} \, s^{-1}$ is closest to which of the following values in meters?

The wavelength of $H_{\alpha}$ line of Balmer series is $X \ \mathring{A}$. What is the wavelength of $H_{\beta}$ line of Balmer series?

If an electron is moving in the $n^{th}$ orbit around the nucleus with a velocity $v$ and radius $r$,then the value of $n$ is .........

In the Bohr model of an atom, the radius of a hydrogen atom in the ground state is $r_1$ and the radius of a $He^{+}$ ion in the ground state is $r_2$. Which of the following is correct?

The ratio of the lowest energy in terms of wave numbers of the Balmer and Lyman series of lines of the atomic spectrum of hydrogen is