Pressure in gas discharge tube was kept

Explanation

In gas discharge tubes, low pressures are maintained. A common pressure range is around 1 torr. Therefore, option (b) 1 torr is a typical pressure used in gas discharge tubes.Reasons for using 1 torr in experiment:Balance between sufficient ionization and collision avoidance:At pressures too high (e.g., 10 torr), gas molecules become more abundant, increasing collisions between them and cathode rays. This reduces the mean free path of the rays, meaning they interact with gas molecules more frequently, losing energy and failing to reach the screen or detector.At pressures too low (e.g., 0.1 torr), there are fewer gas molecules for ionization, potentially reducing the number of emitted cathode rays and the overall intensity of the experiment.1 torr offers a good balance. There are enough gas molecules to enable sufficient ionization and emission of cathode rays, while the mean free path remains long enough for the rays to travel and be observed without excessive energy loss.