What are Canal Rays?
A Canal ray (also known as a positive or anode ray) is described as a positive ions' beam, created by certain gas-discharge tube types. These rays were observed in 1886 in Crookes tubes when the German scientist named "Eugen Goldstein performed experiments."
Later on, anode rays work by the scientist Wilhelm Wien and J. J. Thomson led to the mass spectrometry development. So, it is said that Dempster is the one who discovered canal rays. He was also one of the first spectrometers to use such ions’ sources.
Canal Ray Experiment
The canal rays experiment is the one that led to the discovery of the proton. The proton discovery has happened after the electron discovery has further strengthened the structure of the atom. In this experiment, Goldstein happened to apply a high voltage across a discharge tube that had a perforated cathode. Also, a faint luminous ray was seen extending from the holes of the back of the cathode.
Apparatus of the Experiment
The apparatus of this experiment includes the same cathode-ray experiment, made up of a glass tube containing two metal ion pieces at different ends that acts as an electrode. These two metal pieces are further connected with an external voltage. The air evacuation lowers the pressure of the gas present inside the tube.
The Procedure of the Experiment
Let us discuss more details about the procedure of the experiment, as listed below.
As the apparatus is set up by evacuating the air and giving a high voltage source for maintaining a low pressure inside the tube.
The high voltage is passed to the two metal pieces to ionize the air by making it an electricity conductor.
Thereby, the electricity starts to flow as the circuit is complete.
When the voltage was increased to thousands of volts, a faint luminous ray was seen, extending from the holes present behind the cathode.
These rays moved in the opposite direction facing the cathode rays and were called canal rays.
Explanation
When a higher voltage is applied, the experiment ionizes the gas, and it is the positive ions of gas that constitute the canal ray. It is the kernel or nucleus of the gas that is used in the tube, and thus, it has different properties to that of the cathode rays, made up of electrons.
Differences between Cathode and Anode Rays
Basically, in the first Canal ray experiment, William used the Crookes tube supplying high voltage and gradually reduced the pressure within the tube chamber from 0.01 to 0.001 atm. Also, he noticed a certain beam of light starting to emanate from the tube's cathode, and this travelled throughout the tube upon reducing the pressure further.
Then, the light emitted from the ray was passed via the strong electric field formed between two plates, charge positive and negative. The light beam was found to curve towards the positive plate and was thus charged negatively. It was named Cathode Rays because it originated from the Cathode of the Tube.
After that, using a perforated Cathode (Cathode with fine pores), he conducted another experiment. Even this time, too, he saw the light, but now, starting from the middle of the tube. Upon increasing the voltage and reducing further pressure, the beam went towards the cathode. The beam bent towards the negative plate when the light beam was placed in between an electric field, and hence, these rays were charged positively.
But we cannot call them Anode Rays since they weren't emitted from the AnodeAnode. Therefore, they were known as Canal Rays because they formed light 'canals' when they left the cathode's perforations.
Production of Anode Rays
When a high range of voltage is applied to the tube, the electric field accelerates the small ions count (electrically charged atoms) that are always present in the gas, created by natural processes like radioactivity. These collide with the gas atoms by knocking the electrons off of them and creating added positive ions. These electrons and ions strike more atoms, in turn, creating added positive ions in a chain reaction. Then, all the positive ions get attracted to the negative cathode, and a few of them pass through the holes in the cathode if any. These are known as the anode rays.
Conclusion
Unlike the cathode rays, canal rays will depend upon the nature of gas that is present in the tube. This is due to the canal rays being composed of positive ionized ions formed by the ionization of gas present in the tube.
The charge to the ratio of mass for the ray particles was different for different gases.
The particle's behavior in the magnetic and electric fields was opposite compared to the cathode rays.
Besides, a few particles that are charged positively carry multiples of the fundamental value of the charge.
E. Goldstein also concluded that apart from the cathode rays that pass from the negatively charged electrode to the positively charged electrode, there is another set of rays that move exactly in opposite directions which is from a positively charged electrode to a negatively charged electrode and these rays are canal or anode rays. They were further analyzed and it led to the discovery of a positively charged subatomic particle called “Proton”.
FAQs on Canal Ray Experiment
1. What was the Canal Ray Experiment conducted by Goldstein?
The Canal Ray Experiment, performed by Eugen Goldstein in 1886, was a modification of the cathode ray tube experiment. He used a discharge tube with a perforated cathode (a negative electrode with holes in it). When a high voltage was applied, he observed faint rays travelling in the opposite direction to the cathode rays. These new rays passed through the 'canals' or holes in the cathode, so he named them canal rays.
2. What are the main properties of canal rays?
Canal rays have several distinct properties that help us understand their nature. The most important ones are:
- They consist of positively charged particles.
- They travel in straight lines.
- Unlike cathode rays, their mass and charge depend on the type of gas taken inside the discharge tube.
- They can produce fluorescence on certain materials.
- They are deflected by electric and magnetic fields, but in the opposite direction to cathode rays.
3. How are canal rays actually produced inside the tube?
Canal rays are not emitted from the anode. Instead, they are produced in the space between the anode and cathode. The high-speed electrons (cathode rays) collide with the neutral gas atoms present in the tube. These collisions are energetic enough to knock electrons out of the gas atoms, turning them into positively charged ions. These newly formed positive ions are then attracted towards the negative cathode, forming a beam of rays known as canal rays.
4. What is the most important conclusion from the canal ray experiment?
The most significant conclusion from the canal ray experiment was the discovery of the proton. The experiment proved the existence of positively charged particles within the atom, leading to the idea that atoms were not indivisible but were made up of smaller subatomic particles. This laid the groundwork for a more detailed model of the atom.
5. Are canal rays and anode rays the same thing?
Yes, canal rays are often referred to as anode rays. This is because they are positively charged and move away from the positive anode towards the negative cathode. However, the term 'canal rays' is more descriptive, as it refers to how they were observed passing through the channels or 'canals' in the perforated cathode. It's important to remember they don't originate from the anode itself.
6. How do canal rays and cathode rays differ from each other?
Canal rays and cathode rays are essentially opposites. The main differences are:
- Charge: Canal rays are positively charged, while cathode rays are negatively charged.
- Composition: Canal rays are composed of positive ions of the gas in the tube, while cathode rays are composed of electrons.
- Mass: The mass of canal ray particles varies depending on the gas used. The mass of cathode ray particles (electrons) is always constant.
7. Why does the mass of canal rays change when you change the gas in the tube?
This is a key concept that distinguishes canal rays from cathode rays. Canal rays are formed when gas atoms lose electrons and become positive ions. Since atoms of different gases (like hydrogen, helium, or neon) have different masses, the positive ions formed from them will also have different masses. For example, a hydrogen ion will be much lighter than a helium ion. In contrast, cathode rays are just electrons, which have the same tiny mass no matter which gas they come from.
