Question

When a high voltage of about 10000 volts is applied to a discharge tube having a perforated cathode and containing air at very low pressure of about 0.001 mm of mercury, a faint red glow is observed behind the cathode.
What were the conclusions of this experiment ?
i. Anode rays are positively charged.
ii. Since these rays are formed at the anode, they are known as anode rays.
iii. The experiment led to the discovery of electrons.
iv. The experiment led to the discovery of protons.

• A. i, ii and iii
• B. ii, iii and iv
• C. i, ii and iv
• D. i, iii and iv

Answer 1

The correct option is C i, ii and iv

It was observed that when a high potential difference was applied b/w the electrodes, not only cathode rays were produced but also a new type of rays were produced simultaneously from anode moving towards cathode and passed through the holes or canals of the cathode. These rays were termed canal rays since these passed through the canals of the cathode.These were also named anode rays as these originated from anode.
When the properties of these rays were studied by Goldstein, he observed that these rays consisted of positively charged particles and named them as positive rays.
The following characteristics of the positive rays we recognised :
(i)The rays travel in straight lines and cast a shadow of the object placed in their path.
(ii) Like cathode rays, these rays also rotate the wheel placed in their path and also have heating effect. Thus, the rays passes K.E. i.e. mass particles are present.
so this experiment says,
i. Anode rays are positively charged.
ii. Since these rays are formed at the anode, they are known as anode rays.
iv. The experiment led to the discovery of protons.