The wavelength of a spectral line emitted is inversely proportional to:

The ionization energy of a singly ionized helium ion $(He^+)$ is equal to:

Which of the following corresponds to the energy of a possible excited state of hydrogen (in $eV$)?

The angular momentum of the $2^{nd}$ Bohr orbit of the $H$ atom is $x$. Find the angular momentum of the $1^{st}$ excited state of $Li^{+2}$.

$A$ source of monochromatic radiation of wavelength $400 \, nm$ provides $1000 \, J$ of energy in $10 \, seconds$. When this radiation falls on the surface of sodium,$x \times 10^{20}$ electrons are ejected per second. Assume that wavelength $400 \, nm$ is sufficient for ejection of electrons from the surface of sodium metal. The value of $x$ is $......$. (Nearest integer) $(h = 6.626 \times 10^{-34} \, Js)$

The energy of the second orbit of a hydrogen atom is $-5.45 \times 10^{-19} \ J$. What is the energy of the first orbit of $Li^{2+}$ ion (in $J$)?