The dual nature of photons is described by:

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:

The potential energy of an electron in the hydrogen atom is $-6.8 \ eV$. Indicate in which excited state the electron is present.

Choose the correct option regarding: Assertion: Energy of the orbital decreases with increase of $n$.
Reason: Energy is required in shifting away the negatively charged electron from the positively charged nucleus.

Electrons with a kinetic energy of $6.023 \times 10^4 \ J/mol$ are evolved from the surface of a metal when it is exposed to radiation of wavelength $600 \ nm$. The minimum amount of energy required to remove an electron from the metal atom is

Calculate the energy of an electron in the first four orbits of a hydrogen atom in $kJ \, mol^{-1}$ (Given: $N_A = 6.02 \times 10^{23} \, mol^{-1}$,Rydberg constant $R_H = 2.18 \times 10^{-18} \, J$).