prac: investigating discharge tubes (1 Viewer)

[d00d]

hey at school we're up to ideas to implementation and we've done a prac to investigate the effect of different pressures on cathode rays.

however, our apparatus is shoddy, so the results aren't very good. anyone else done this expt?

could u plz give me the correct answers or the URL to model answers. i need diagrams of 40mm, 10mm, 6mm, 3mm, 0.14mm and 0.03 mm Hg (mercury) tubes. plz label features such as dark spaces. also do u have a URL that explains these effects, i know its something to do with electron excitation but i can't find any resources on it. thx.

 

[d00d]

the excel book covers it very briefly... anyone else?

 

[d00d]

bump

 

[d00d]

bounce

 

[McLake]

*sproing*

OK, this is an annoying experiment, and I'm bound to say something slighty wrong here, but they go like this:

At one end of the spectrum (lowest pressure) you have a yellow/green glow down the whole tube. This progress to a pikn purple glow with a few striation, the smaller and smaller (but larger amounts) of striations, then finally at the "high" pressure end you get "streamers" (like little lightning bolts) of electricity ...

 

[d00d]

can u plz explain these results? like what causes the streamers and striations...

 

[McLake]

The streamers are caused by the extremly high energy of the electrons that make it across the gap. The striations are caused by the slighty less energetic electrons that make it across the slightly easier gap.