For the Paschen series, the values of $n_1$ and $n_2$ in the expression $\Delta E = R h c \left( \frac{1}{n_1^2} - \frac{1}{n_2^2} \right)$ are:

What transition in the hydrogen spectrum would have the same wavelength as the Balmer transition $n=4$ to $n=2$ of $He^{+}$ spectrum?

According to Bohr's atomic theory :-
$A$. Kinetic energy of electron is $\propto \frac{Z^{2}}{n^{2}}$.
$B$. The product of velocity $(v)$ of electron and principal quantum number $(n)$,'$vn$' $\propto Z^{2}$.
$C$. Frequency of revolution of electron in an orbit is $\propto \frac{Z^{3}}{n^{3}}$.
$D$. Coulombic force of attraction on the electron is $\propto \frac{Z^{3}}{n^{4}}$.
Choose the most appropriate answer from the options given below :

Explain the phenomenon of black body radiation.

The wave number of the spectral line in the emission spectrum of hydrogen will be equal to $\frac{8}{9}$ times the Rydberg's constant if the electron jumps from

Which of the following statements regarding the energy of the stationary state is true in the following one-electron system?