To cause a beam of particles to form an image on a fluorescent screen Strong magnetic fields achieved using superconducting electromagnets (4 T in strength)
The electrons can then be deflected by a magnetic (or in the case of oscilloscopes, an electrical) field (D) before they strike the phosphorescent screen (E), creating an image. Also, the low-pressure air tends to put a limit on the electrons' speeds, affecting the electrons' motions to more closely follow the electric field.Figure 1: The cathode ray tube is a vacuum tube in which electrons are produced by a heated filament (the cathode, A), focused into a beam as they pass through the aperture of the control grid (Wehnelt cylinder, B) and accelerated by the voltage (VA) between the cathode and the anode (C). Like a ball falling in gravity, the electrons are on parabolas, but there isn't much transverse velocity, so like a ball falling straight down, the parabolas are just lines. The electrons travel in straight lines (or nearly straight curves) because the electric field between the anode and cathode is approximately uniform, that is, straight lines. So, we need a bit of air so something interesting happens, but not enough that it gets in the way. You'd see a small area of glow right around the cathode, perhaps, depending on conditions. Normal air suitable for everyday human use would involve so many interactions in a short distance, the electrons be scrambled into a fuzzy cloud of plasma, and not make it to the anode but by an uninteresting, undramatic process of diffusion through the air. The electrons would be deflected and lose a small part of their kinetic energy with each interaction. It can't be air at normal pressure, because that would be too many molecules in the paths of the electrons. That's why the glass tube isn't just a plain vacuum. To have the electron-molecule interactions, of course we need molecules. This is usually much stronger than needed to merely ionize air molecules - we want to those electrons to fly to the anode rather than be scattered by their interactions with the molecules. A stronger field is made by a higher voltage difference applied to the anode and cathode.
How fast they move is determined by the strength of the electric field. Note that the concept of flourescence isn't relevent.įor the electrons emitted by the cathode to do this, they need enough oomph. In a short time, seconds or a fraction of a second, these electrons rejoin the ionized molecules, fall back into the ground states through one or more quantum decays emitting photons.
#CATHODE RAY TUBE EXPERIMENT IN HIGH SCHOOL FREE#
The negative electrons are pulled strongly enough by the positively charged anode that they whack the electrons in the O2 and N2 molecules, putting them into higher energy states or knocking them free of the molecule. The light emitted from the electron stream comes from nitrogen and oxygen molecules. I know the questions are very silly but because different websites refer to different things, I am becoming confused with something that should be simple to understand. Could someone please tell me why these conditions were necessary? For example, " The cathode rays consist of material particles because they produced shadow of objects placed in the way"ģ.Two of the conditions of the experiment were air at very low pressure and secondly a very high potential difference. The path cathode rays travel is not affected by the position of the anode." I just can't seem to understand this explanation of the one of the observations.Also, different websites analyses this observation differently. That is why, cathode rays cast shadow of any solid object placed in their path. Is this the color of the radiation itself?Ģ." Cathode rays travel in straight lines. However, as shown in the above diagram there was no fluorescent material in the experiment carried out first on the cathode ray tube. Many websites I read through refer to a fluorescent material.
1.One of the observations I learned was that the glass tube begins to glow with a brilliant green light.
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