Why for the ionization of gas,lower pressure is more favoured than high as in the discharge tube?
High pressure means more particles to be ionized then what is the reason behind this?
In a discharge tube, lower pressure is more favored for ionization of the gas compared to higher pressure. This is due to a phenomenon called the Paschen's Law.
Paschen's Law states that the breakdown voltage (the voltage required for ionization of the gas) is inversely proportional to the product of the pressure and the distance between the electrodes. In other words, as the pressure decreases, the breakdown voltage decreases for a given distance between the electrodes.
The reason behind this behavior is related to the collision frequency of gas particles. At higher pressures, there are more gas particles in a given volume, resulting in a higher collision frequency between the particles. These collisions can disrupt or neutralize the electric field required for ionization, making it more difficult for the gas to become ionized. Additionally, at higher pressures, there is a higher chance of recombination of ions, where ions may recombine with free electrons, preventing ionization.
On the other hand, at lower pressures, there are fewer gas particles in a given volume, resulting in a lower collision frequency and reduced chances of recombination. This enables the electric field to more effectively ionize the gas, leading to a lower breakdown voltage.
Therefore, in a discharge tube, lower pressure is more favored for ionization due to the reduced collision frequency and decreased chances of recombination, allowing for easier and more efficient ionization of the gas.