Crookes Maltese Cross tube

[oskaras77]

thats iron cross of german army not the maltese cross...

[HorizonDelta]

Kool !

[JRussoBuffaloNY]

Tis' a cross pattee', not a maltese cross.

[Shiboneko]

now it's broken

[davideoking101]

we are studdieing this is school, anyone out there know why the image of the cross is there after it fell?

[ivanlagrossemoule]

@davideoking101 They use coating that reacts to the electrons to produce light. That coating doesn't last forever and it gets used over time. The coating behind the cross isn't as used and therefore produces more light. If you want more details you would probably have to look up how the coating's chemistry works.

[western582]

@davideoking101 I think initially the light streaming was blocked by the cross and all the light received was due to diffraction and reflection from the glass tube but when the cross was put down,the rays directly reached increasing the intensity of the light!!

Or else simply we can put it as persistence of the fluorescence!!!

[ivanlagrossemoule]

Had some of them at school. The teacher told us that they had some really beautiful ones a few years ago. But they were ancient (the college where I used to go was centuries old). One day some guys came and found out they were dangerously radioactive so they had to remove them from the school. Now I'm looking for some people on youtube who don't care about their lives and still use them.

[AlastairWright]

@ivanlagrossemoule

It's a shame they were removed from your school. I wonder if the people who removed them sold them as some of these tubes are worth a lot of money. There's a confusion here as the tubes are definitely not radioactive. However some tubes with an extreme high vacuum emit X-rays when powered up and shouldn't be used in schools.

[ivanlagrossemoule]

@AlastairWright Now I think about it, it must be X-rays. I remember he told us that they were hundreds of times over the accepted limit.

Oh well, we still had some nice ones to see.

I don't think they were sold though. Either they were stored somewhere in the college, but if they were they must have cost a fortune.

[iTechRevolutionTV]

@AlastairWright Here in Belgium , they don't support so much of science. and I love science but in our school there is like 1 or 2 material for 1- 6 grades

[eolsunder]

yep watch it again, watch the shadow on the glass when the cross drops, the shadow instantly turns brighter, like its lit up. very cool

[EpicPilloww]

So the production of a sharp shadow hints at the fact that its a stream of light?

[AlastairWright]

@EpicPilloww a stream of something, electrons in fact.

[AlastairWright]

@KX36

You obviously don't have any idea what is happening in the video.

[KX36]

@AlastairWright Oh, I wasn't really paying attention, I thought you accidentally knocked it. hehe

[AlastairWright]

@KX36

No, it's part of the function of the tube and that's why the aluminium Maltese Cross is hinged. The glass glows much brighter where the shadow of the cross was.

[giakful]

I would love to have this object. where can I buy it?

[Laevi1337]

wow, so now i know where the name for my final approach fixes on non precision approaches comes from

lol

[M4Z0RK1ZT4]

What happen if this ray touch your skin?

[QuickiStick]

Thank you, the maltese cross wouldn't work in class as the equipment was broken.

This video has been very helpful to my learning :)

[XELA2T]

Very nice demo, very nice CRT and very good explanations you give in your comments.

[AilleCross]

What makes the glass fluorescent? Is there uranium in the glass that reacts to the electron stream? Or is the electron stream from the cathode ray naturally fluorescent green? I am learning about historical scientific instruments for a book, and this video has been very helpful already, thank you.

[AlastairWright]

This is plain soda glass and not uranium glass. The cathode stream produces X-rays when they strike the glass and it's the X-rays that make the glass glow green. Other glasses glow different colours in cathode ray tubes. Lead glass fluoresces pale blue and didymium glass glows red.

[mpramirezz]

Where did you buy the very nice induction coil?

[cybermecium]

I love the old school induction coil setup. Reminds me of the "Violet Ray" "medical" devices I picked up at a couple garage sales..

[2N2222A]

Far out! Always seen pics in the books, but you really did it.

[davematthewsblows]

hey man i caught the clap from some chick. can i have one for free too? we can be friends as well.

seriously tho, is that low iron glass?

[CamiloSanchez1979]

why does it bright even more when the cross falls down??

[AlastairWright]

What is happening is that the glass is slowly damaged by the impact of the high energy electrons. This radiation damage slowly degrades the fluorescence properties of the glass. Because the glass in the shadow of the cross receives less total dosage, it is in better shape. Thus, when you lower the cross, the glass that was shadowed glows brighter. This phenonena is essentially identical with the "burning" you see on CRT computer monitors. If you have some bright text that is always

[CamiloSanchez1979]

thank you sir...

[MSVistasucks]

So eventually the tube will be no good.

[frankensteinmoneymac]

I want one. I want it because I am dying of liver failure and it is my last request. I have no money to give you but you would have my friendship. If that doesnt work then I can make up some other disease to pretend to have. None the less I really want one of these, and although I would prefer you to give it to me of your own free will, I may be willing to purchase one. Where can I find one, or is yours for sale??

[m3sca1]

saw plenty of drawings of this device-but didnt understand what it was for until i saw it working -thanks for sharing your amazing collection

[hacker126]

in 9th grade my Physical Sci teacher wouldnt run his in the class because when the electrons hit the metal i guess it releases xrays in a high amount (im quoting my science teacher if im wrong please tell me )

[saintaureus]

Crookes tubes can create x-rays if the voltage is high enough.

[skuitarman]

were did you get the power supply???

[fullrangechris]

nice induction coil

[alextzam]

where can i buy one of this?

[AlastairWright]

If you get green glass fluorescence then you're getting X-Rays, that's my understanding.

Better ask Sci-Supply about their tubes, I would be interested to hear their reply.

[ccameron777]

All this talk of X-Rays was making me a little leary of purchasing this tube. I've been told that with a cap at 5KV, X-Ray radiation will not be a problem. Is this correct? I've found a tube at Sci-Supply for a reasonable price that I want to purchase, but need some guidance on input. Does anyone have any info on the input limits (KV). Go to sci-supply to see the tube I want if it helps, but they have no info on input requirements. Help...

[JonasClark]

The glass itself fluoresces where the electrons strike it. Some Maltese Cross tubes (newer ones) have a blue-green phosphor painted there. This one does not. The glass around the shadow area gets used to the bombardment quickly - so when you drop the mask (cross) the formerly-shadow area glows brighter for a moment.

[JonasClark]

The green glow isn't uran-glass, it's the fluorescence of the glass wall, caused when electrons/cathode rays strike it. In any Crookes tube with this sort of low pressure, the green glow indicates the production of x-rays, usually very soft ones. "Uran-glass" means uranium oxide glass, which is tinted pale green, and which fluoresces when a discharge takes place. It is usually seen in Geissler tubes, which have a higher pressure and usuallycannot produce cathode rays or x-rays.

[vmelkon]

I think there is some coating inside the glass. When he pulled down the cross, the cross area on the glass glows a lot. That area, the phospor is ok and the rest is damaged phosphor, maybe?

Or maybe it is just glass.

Anyway, last time I tried this sort of thing, the glass glowed blue green. 15KV electron beam.

[anonym10000]

"its the uran-glass..it too glows green by x-rays.." -> means the same...@ Xanthosine

i dont wanna copy wikipedia^^ !

[Xanthosine]

All this talk of x-rays is just clouding the issue. Crookes Catlese Cross experiment demonstrates (along with further adaptaions) the existence and nature of cathode pays - that is the nature of the ELECTRON. Yes, x-rays are produced but the glow is due primarily to cathode rays, emitted from the cathode - ie electrons, smashing into the glass. This is proven by their magnetic deflection. X-rays would not be deflected.

[AlastairWright]

Yes :)

I'm glad somebody understands.

[piinkpandahh69]

that sounded dangerous

[mapexlb]

thats wierd stuff... I really dont understand where the green is coming from but if you could sustain it that would be dope.

[anonym10000]

its the uran-glass..it too glows green by x-rays..

[Xanthosine]

anonym10000 : "its the uran-glass..it too glows green by x-rays.. "

not a good explanation

[w5cdt]

You can place a used x-ray screen (like the types used in x-ray film packs) near the Crookes tube to check for x-rays. Should

glow green.

[RotogenRay]

Hmm, how strong are those x-rays?

What kind of power supply is that anyhow?

[AlastairWright]

X-rays are strong enough that these tubes aren't used in school classrooms any more.

The power supply is an induction coil.

[RotogenRay]

well, considering the way our govornment works, I wouldn't be surprised if regular CRT TVs were soon outlawed for the tiny bit of x-rays they produce. And the fact that they're a disposal hazard with the phosphorous and lead present in them.

But some kind of guesstimate on the rads or watts or something of the x-rays would be nice, if you could guess at all.

And I suspected it was an induction coil, but I was inquiring more about the voltage of the transformer (coil).

[clerlic]

I don't think regular TV's will be outlawed any time soon, as long as they're cheaper and more available than LCD or plasma TV's, they're a nice way to spread government messages all over the country.

[RotogenRay]

well there's that.

and there's also anti-taco legislation.

go figure, you know...

[gabydewilde]

hahaha

[RotogenRay]

The paradigm shift is away from CRTs to lcd and plasma screens. The whole ROHS (reduction of heavy substances) doesn't like the lead in the glass

As well, the panzies don't like that "we might get irradiated"

You get more radiation walking outside than from watching tv

And I would argue that the more destructive force is the programming on the TV...

[orangetide]

The lead is supposed to shield you from the X-rays. leaded glass is also fantastic for other reasons.

[veryvexed]

ahhh! that doesn't look like uranium doped glass and its glowing pretty bright, careful of teh x-rays! i like your viddys!

[AlastairWright]

I'm aware of the x-rays, you see how short this video is? Glad you like them, watch this space there'll be more posted sometime....

[gabydewilde]

thanks for risking your life in the name of science :0)