Question

In a discharge tube ionization of enclosed gas is produced due to collisions between :

• A. positive ions and neutral atoms / molecules
• B. negative electrons and neutral atoms / molecules
• C. photons and neutral atoms / molecules
• D. neutral gas atoms / molecules

Answer 1

The Correct Option is B

To solve this question, we need to understand the process of ionization in a discharge tube.

In a discharge tube, ionization of the gas is a crucial step where neutral atoms or molecules gain or lose electrons, forming ions. This process primarily occurs due to collisions between different particles present in the tube.

Let's analyze each option provided to identify which one is most likely responsible for ionization:

1. Positive ions and neutral atoms/molecules: While positive ions can cause some ionization by colliding with neutral atoms, they are not the primary source of ionization in a discharge tube.
2. Negative electrons and neutral atoms/molecules: This is the correct answer. Electrons, especially when accelerated by an electric field in a discharge tube, have sufficient energy to collide with neutral atoms/molecules. These collisions can lead to the ionization of the gas by knocking out electrons from the atoms, thus producing ions.
3. Photons and neutral atoms/molecules: Ionization by photons occurs in photoionization processes, but it is not the primary mechanism in a typical discharge tube under consideration.
4. Neutral gas atoms/molecules: Collisions between neutral atoms/molecules themselves do not lead to ionization as they do not have sufficient energy to ionize each other.

Hence, the primary mechanism of ionization in a discharge tube is due to the collisions between negative electrons and neutral atoms/molecules, which provides the necessary energy to ionize the gas.