-3
$\begingroup$

A Crooke's Tube is a cold-cathode tube, wherein electrons are released from the cathode when ionised gas particles strike it with speed. Following a chain reaction, other gas particles also get ionised over time and do the same. But I guess there would be a time when all the gaseous atoms would have been ionised and travelled towards the cathode. So, no more electrons should be released now...and thus no cathode rays.

Or is there something happening, like the ionised atoms becoming normal again. It arises one more question in my mind....what happens to the ions after they strike the cathode?

$\endgroup$
1
  • 2
    $\begingroup$ If only it were that easy to make ultra high vacuum. Sadly, your chamber outgasses material and you need to keep pumping on it to just maintain the vacuum. $\endgroup$
    – Jon Custer
    Jun 3 at 18:24
2
$\begingroup$

Over time, the residual pressure in a gas discharge tube does drop. One of the main causes for gas loss is sputtering. Ions sweep gas atoms from the tube and embed them in metal sputtered from the cathode, as does an ion vacuum pump.

For this reason, neon and fluorescent lamps show a gradual increase in voltage required to sustain the glow discharge, and the glass near the electrodes gradually darkens from sputtered metal.

However, loss of ions is not an issue - if atoms are broken apart into electrons and ions at one end of the discharge tube, they're happily reunited at the other end - though with different electrons. Of course, in the dark (discharge), all electrons look the same.

$\endgroup$
5
  • $\begingroup$ okay...thanx a lot $\endgroup$
    – user95732
    Jun 4 at 10:29
  • $\begingroup$ If the cations recombine with the electrons, then won't they release energy in form of light....as happens in glow discharge (negative glow) $\endgroup$
    – user95732
    Jun 5 at 6:18
  • $\begingroup$ @user95732, Absolutely! It's called the cathode glow, merriam-webster.com/dictionary/cathode%20glow . Furthermore, when high-energy electrons and ions smash into the electrodes, they release other wavelengths than visible light, i.e., X-rays. This is from braking, or Bremsstrahlung, radiation. (should have an eszett, not ss, IMHO). $\endgroup$ Jun 6 at 1:48
  • $\begingroup$ Gotcha! But please tell me one thing more...when these electrons (cathode rays) strike the glass wall, some are transmitted, some absorbed and some reflected. What does absorption mean? Do the electrons loose all their energy in exiciting the electrons of glass atoms....and stop midway in the glass? Can they stop midway in the glass, between the atoms? $\endgroup$
    – user95732
    Jun 6 at 2:54
  • $\begingroup$ @user95732, yes,right again! Electrons and ions can be implanted into solids. In non-conductive materials, ionic defects (F-centers, en.wikipedia.org/wiki/F-center), Frrenkel defects, en.wikipedia.org/wiki/Frenkel_defect and hole-centers, minsocam.org/msa/collectors_corner/arc/color.htm, can cause coloration, as in quartz or diamonds exposed to ionizing radiation. Of course, if enough charge builds up, the material would arc over internally, even though it is a nonconductor. See caratsdirect2u.com/Articles.asp?ID=278 $\endgroup$ Jun 6 at 19:38
1
$\begingroup$

When ions strike an electrode, they are discharged and become electrically neutral. Cations, or positive ions, are attracted by the cathode (negative pole). Anions, or negative ions, are attracted by the anode (positive pole). Once discharged, they may again go into the gas phase, with or without chemical change.

$\endgroup$
2
  • $\begingroup$ The chamber was just start leaking gas,so it makes it useless. $\endgroup$ Jun 4 at 3:08
  • $\begingroup$ thank you for ur answer $\endgroup$
    – user95732
    Jun 4 at 10:29

Not the answer you're looking for? Browse other questions tagged or ask your own question.