If the ionization energy of $He^{+}$ is $8.68 \times 10^{-18} \ J$,then the energy of $Be^{3+}$ ion in the second orbit is:- ($Z$ of $Be = 4$)

If the Thomson model of the atom was correct,then the result of Rutherford's gold foil experiment would have been:

If the energy of the first orbit of $He^{+}$ is $-54.4 \, eV$,then the energy of the second orbit will be ............. $eV$.

$A$ photon of wavelength $4 \times 10^{-7} \, m$ strikes on a metal surface. The work function of the metal is $2.13 \, eV$. Calculate:
$(i)$ The energy of the photon in $eV$.
$(ii)$ The kinetic energy of the emission in $eV$.
$(iii)$ The velocity of the photoelectron in $ms^{-1}$ ($1 \, eV = 1.6020 \times 10^{-19} \, J$,mass of electron $m = 9.10939 \times 10^{-31} \, kg$).

The value of the work function of a metal $X$ is $3.1 \ eV$. What is its threshold frequency (in $Hz$)? (Given: $h = 6.62 \times 10^{-34} \ J \cdot s$)

Bohr’s atomic theory gave the idea of :