In a $He^{+}$ ion,an electronic transition occurs from orbit $n_2$ to $n_1$ such that:
$2n_2 + 3n_1 = 18$
$2n_2 - 3n_1 = 6$
What is the total number of photons emitted when the electron transitions to the $n_1$ orbit?

The value of Planck's constant is $6.63 \times 10^{-34} \ J \ s$. The velocity of light is $3.0 \times 10^8 \ m \ s^{-1}$. Which value is closest to the wavelength in nanometres of a quantum of light with frequency of $8 \times 10^{15} \ s^{-1}$?

The radius of the $2^{nd}$ orbit of $B^{4+}$ ion is:

Which transition in the hydrogen atomic spectrum will have the same wavelength as the transition,$n = 4$ to $n = 2$ of $He^{+}$ spectrum?

$A$ metal having a work function of $4 \, eV$ is exposed to a photon of $\lambda = 1240 \, \mathring{A}$. If an accelerating potential of $7.6 \, V$ is applied,then the electron with maximum kinetic energy will have a speed equal to -

The frequency of the first line of the Paschen series in the spectrum of the $Be^{+3}$ ion is: