Question

Explain emission and absorption spectra.

Answer 1

Hint: The difference in different energy levels of an atom can be found using the formula: ${{E}_{1}}-{{E}_{2}}=h\vartheta =\dfrac{hc}{\lambda }$. The difference in the energy level, leads to emission or absorption of photons, having characteristic wavelength (or) frequency for the transition between the energy levels. The emission spectra are created by the characteristic photons emitted due to excitation and de-excitation phenomenon of the gas. The absorption spectra is created by the absorption of characteristic frequencies by a range of electromagnetic spectrum.

Complete step-by-step answer:
The emission and absorption spectra are shown by atoms of different elements. It’s also important to know that emission and absorption spectra of any 2 different atoms aren’t the same. The reason being, these absorption and emission spectra arise due to the configurations of the energy levels in each atom. Since, the configurations of the energy levels of each atom differs from the other, hence the emission and absorption spectra of each element differ from other. Hence, they are unique to each element.
The difference in different energy levels of an atom can be found using the formula: ${{E}_{1}}-{{E}_{2}}=h\vartheta =\dfrac{hc}{\lambda }$. The difference in the energy level, leads to emission or absorption of photons, having characteristic wavelength (or) frequency for the transition between the energy levels.
Let’s understand the emission spectra now. The emission spectra is emitted by a gas of a certain atom when the electrons of the gaseous atoms absorb enough energy to jump into higher energy levels and then these electrons fall back to their initial energy level. The falling back of the electron from the excited energy level, causes a photon of characteristic frequency to be emitted. Similarly, when higher energy is given to the atom, and if the energy is enough to excite the electrons to an even higher excited level, then a photon, with higher frequency characteristic photon is released.
Therefore, a regular emission spectra has a black background containing lines of the characteristic frequency of the atom to be visible.
Let’s understand the absorption spectra now. The absorption spectra unlike the emission spectra isn’t emitted by the atoms, instead the absorption spectra is created when a light of all the frequencies is shined on the gas of atoms and the atoms absorb the characteristic frequencies and get excited. This causes certain frequencies to be absent when we look at the absorption spectra. Hence, unlike the emission spectra, which only contains characteristic frequency lines against a dark background, the absorption spectra contains a spectra of all the wavelengths, with a few of them missing, which are the characteristic frequencies of the gaseous atom as they were absorbed.

Note:
The use of the emission and absorption spectra are as follows:
The emission spectra is usually used to figure out the composition of the matter. Since, the type of photons emitted reveals information about the kind of element by studying the unique distribution of the energy levels in different atoms.
The absorption spectra is usually used to find the ability of certain objects to retain heat and its absorption level. The frequencies of the light absorbed can also be used to extract the number of substances in a sample.