Why doesn't a neon sign finally run out of excited atoms and produce dimmer and dimmer light?
Because electrons are returning to their ground state in neon atoms (they stay excited for a VERY short time) so there are plenty of neon atoms in the ground state to be re-excited.
A neon sign doesn't run out of excited atoms and produce dimmer light because it operates on a process known as gas discharge. Here is a step-by-step explanation of why this happens:
1. Neon signs are filled with a low-pressure gas, typically neon, but sometimes other gases like argon or helium mixed with a small amount of neon.
2. The gas in the sign is electrically charged by applying high voltage across two electrodes, one at each end of the sign.
3. When the voltage is applied, it helps to ionize the gas atoms, meaning it provides enough energy to remove electrons from the atoms, creating positively charged ions and negatively charged electrons.
4. These ionized atoms collide with other atoms in the gas, transferring energy to them and causing them to become excited.
5. The excited atoms or ions can then return to their ground state by releasing the excess energy they have absorbed.
6. When an excited neon atom releases this energy, it emits light in the form of photons.
7. The emitted light corresponds to a specific wavelength characteristic of the gas being used (in the case of neon, it produces a reddish-orange color).
8. This light continues to be emitted as long as the electrical energy is continuously supplied to the electrodes, maintaining the ionization of the gas.
9. The gas inside the sign does not get used up or depleted during this process. The atoms that have been excited return to their ground state and can be excited and emit light again when provided with the right conditions (i.e., high voltage).
10. Therefore, as long as the electrical energy is supplied to the neon sign, it can continue to emit the same intensity of light with no significant decrease over time.
11. However, over an extended period, the electrodes can slowly degrade due to a process called electrode sputtering, which may slightly decrease the brightness of the sign, but this degradation is gradual and can be accounted for by proper maintenance and periodic replacement of the electrodes.
In summary, a neon sign does not run out of excited atoms because the gas discharge process allows the excited atoms to return to their ground state and be excited again, as long as electrical energy is supplied.
Neon signs don't run out of excited atoms and produce dimmer light because they use a process called gas discharge to create light. In a neon sign, the gas is contained in a sealed glass tube and is filled with low-pressure neon gas. The tube also contains electrodes at each end, typically made of metal, which are connected to a high voltage power supply.
When the power is applied, a high voltage electrical discharge is generated across the electrodes. This causes the gas atoms in the tube to become ionized, meaning that they gain or lose electrons. As the atoms regain their electrons, they emit light in the visible spectrum.
What's interesting is that the excited atoms in the neon gas can stay that way for a long time, even after the electric current is no longer passing through the tube. This phenomenon is known as "afterglow". The afterglow can last for a few milliseconds to several minutes, depending on the gas pressure and the specific gas used in the sign.
So, even though the electric current stops flowing through the tube, the neon gas atoms remain excited and continue to emit light, hence why a neon sign does not dim over time. However, the intensity of the light may gradually decrease due to factors such as gas leakage, electrode degradation, or other aging effects that can occur in the sign. But these are external factors and not a result of the neon gas running out of excited atoms.