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Emission Spectra - Light .. Physics

Emission Spectra

The electrons in the atom are arranged in almost circular orbits, each of which contains a specific number of electrons. Since the number of electrons increases from one element to another, these orbits are filled with electrons starting with the orbit that is closest to the nucleus.

It is worth noting that the energy of the atom is determined primarily by the orbits filled with electrons, and that it increases as the distance separating it from the nucleus increases.

If the atom is able to absorb a certain amount of energy from the surrounding medium, one of the electrons in it becomes able to jump from its orbit to an orbit characterized by a higher level of energy, but on the condition that there is a vacant place for it in this orbit (this is possible for the electrons in the outer orbits because the inner orbits are filled with their specific share). In this case, the atom becomes excited. In 1913, Neil Bohr explained that the absorption or emission of radiant energy by an atom is in the form of photons, each of which has an energy of n, and that the absorption of a single photon leads to a single jump for the electron. Since the excited atom is unstable, the electron then returns to its original orbit, releasing at the same time all the excess energy, which is equal to the difference between the values ​​of its initial energy and its final energy, Q1 - Q2. This released energy takes the form of a photon according to the equation Q1 - Q2 = h n. It is worth noting that as a result of the large number of possible orbits, photons will be emitted and will be at different frequencies. When the rays emanating from the hydrogen atom fall on a photographic plate in a spectrograph, a group of thin lines appear on the plate called the emission spectrum of the atom, and each line represents a specific frequency. It is worth noting that each element of matter is distinguished by its own spectrum. Gaseous bodies have their own distinctive linear spectra, while liquids are subject to intense interactions between their atoms and molecules, leading to a slight change in their energy levels. The linear spectrum soon turns into another type of spectrum called the strip spectrum. In solid bodies, these interactions are much greater, which increases the width of the spectral bands that intertwine with each other and form a continuous spectrum. It is known that the light emitted from a hot tungsten filament is a continuous spectrum that covers the entire visible wave section. When the atom absorbs a sufficient amount of energy, the electron can escape from it, becoming a stray (ionized) atom with a positive charge. (The electrons jumping from the higher orbit to the lower orbit form the lines of the hydrogen emission spectrum. (Far right) Comparison between the continuous emission spectrum and the linear emission spectra.