Question

Three energy levels of an atom are shown above. Atoms in the n = 2 state can spontaneously emit photons having which of the following energies?

• A. 7 eV only
• B. 4 eV only
• C. 3 eV and 4 eV only
• D. 3 eV and 7 eV only
• E. 3 eV, 4 eV, and 7 eV

Answer 1

The correct option is B 4 eV only

The photon is emitted when an electron in higher energy state comes to the lower energy state in an atom i.e from $n=2$ to $n=1$ state.

Also from figure: $E_2=4eV$, $E_1=0eV$

$\therefore$ Energy of photon emitted, $E=E_2-E_1=4-0=4eV$ only.