Lovely meeting you too, becky
Not entirely sure. You see I think it was always tacitly assumed I'd end up being a physicist. Trouble is, now I am one I'm not sure I want to carry on being one. Maybe I just need a change of field, possibly even a change of science, but part of me thinks that if I get out the other end of this PhD without being committed then I should get a complete change of scenery, if just for a couple of months, and then the old pipe dream of being a musician rears its juvenile head.

I can keep putting this one off though, with the excuse that I'm never really going to "grow up."
(LongJohnBaldry, Sun 28 Feb 2010, 16:55, 1 reply, 16 years ago)

Heeeeeeeey, I didn't know that. You could end up being the one person viable to explain to me how xray machines work.
Being told that Cathy Cathode and Andy Anode are attracted to each other and cause a cloud of electrons - or neutrons, I'm not really sure - and that then creates the image strikes me as more dumbing down than is strictly necessary. Just the basics would help oh dear lecturer. I think the problem is that she's been taught it in this way and thus knows no other way to relate physics to her students.

I reckon you should be a physics teacher and wear leather elbow pads with tweed every day. In your spare time you could form a blues band and sing songs about particles and complicated equations. Yes.
( fuck shit up the best you never had, Sun 28 Feb 2010, 17:10, Reply)

Funny you should say that, I am wearing a corduroy shirt at present - only a short step from tweed if I understand correctly.
Anyhoo, X-ray machines...they actually work in a surprisingly similarly way to TV tubes, but obviously they produce a very different frequency.

So in a large vacuum tube, you have an "electron gun" which is basically the aforementioned Cathy Cathode pumped up to a very high voltage. "Andy Anode" is some distance away and the aim is to get the electrons to jump across the gap between them. Normally the positive charge of the anode is enough to draw the electrons to it, but you end up with a series of random electrical arcs between the negative cathode and positive anode.

The anode is normally a metal plate with a bevelled (45^o sloped) edge around the outside. For some reason that I can't remember, you can generate X-rays more efficiently if you can get the arcs to strike this sloped edge. So, using magnets to point the arcs in the right direction, these electrons jump across the gap, and dissipate most of this enormous voltage when they land on the anode. About 1% of this energy is given out as X-rays. The sloped edge again comes in handy as most of the X-rays are emitted at an angle of between 60^o and 90^o to the sloped edge.

The X-rays pass through a small window and through your flesh. Those that are not absorbed, scattered or reflected make it through to some sort of detector, which in some cases may just be a piece of photographic film.

I hope that makes sense; admittedly a few of the facts were taken from Wikipedia so may not be entirely reliable. Perhaps your suggestion of physics-teachering is a good one...I spent a while trying to explain to my sister over the phone yesterday why a glass prism splits white light into pretty rainbow colours, so if my attempt to explain X-rays makes any sense then I might take it as a sign!
(LongJohnBaldry, Sun 28 Feb 2010, 17:27, Reply)

OMG Cathy Cathode wants to kill Andy Anode!
We were told a love story about them - yes it was proper feeeelth - but there were just too many silly made up bits that were just put in for the purposes of story telling for it to be any good. So if the KV isn't high enough then the x-rays wont pass through the body to the bones and you'll get a shit looking x-ray because the electrons will have bounced off as scatter, but if it's too high then it'll be over exposed and you'll essentially fry the subject.

Excellent, many thanks Mr Crow :)
( fuck shit up the best you never had, Sun 28 Feb 2010, 17:46, Reply)

A good description
Also, I kind of wish my TV could fire stuff through me. It would be even more impressive since it's a flat screen.
(PenguinOfDeath is Scottish, and most likely angry, Sun 28 Feb 2010, 18:03, Reply)