June 2011 G485-Fields, Particles and Frontiers of Physics

Agh **** sorry for the neg rep. Didnt mean to press that
I did resat unit 2 aswell. but didnt bother with unit 1 and 3.
Have a mid B in unit 1 and was 2ums points off a b in unit3

Do we need to know what quarks and antiquarks make up mesons?

http://www.ocr.org.uk/download/kd/ocr_9587_kd_gce_spec.pdf

I dont think we do, but have a look on the specification ^^^

Pretty much all of it lol.

Mainly ultrasound and x-ray. I don't get anything about ultrasound and don't get some x-ray equations and questions.....thanks.

Ok with ultra sound, the book just goes off on a mad one and i cant really separate the information needed to anser the syllabus statements, please help.

1) Describe the piezo electric effect

Would this be a big mark question?

No, it came up last time as a 2 marker.

here's something on X-ray For you then
X-ray tube: How are x-rays produced in a X-ray Tube and what energy changes take place?

In an X-ray Tube the electrons are emmited from the heated filament (cathode), The electrons are accelerated through a high Potential different in the evacuated X-ray tube towards the Tungston Anode. As the electrons smash into the tungston anode, about 1% of their kinetic energy is converted into X-ray photons. The rest of the 99% of the kinetic engery of the electrons is transffered as heat in the tungston anode. The tungston metal needs to be cooled down due to the bombarding of electrons, so therefore either oil is circulated through the metal or a motor turns the tungston anode to let it cool from one side whilst other parts of the tungston are smashed by electrons. The X-ray photons produced escape through a small window in the led casing in which the X-ray tube is situated. Then the flow of X-ray photons is controlled.

The reason why the X-ray tube is evacuated ( its a vacuum) is because the electrons need a certain amount of engergy to produce X-ray photons as they are decelerated when hitting the tungston anode. So therefore, a vacuum prevents them hitting an gas molecules which would slow them down on the way to the tungston anode.

The is question is worth around 7 to 8 marks but I've given a lot more points for reference.
The process by which electrons are emmited from the cathode in the X-ray tube is called Thermionic emission.

What do you think will be a big mark question?

eurghh i hate G485
medical physics is awful!
been trying to revise electromagnetism...does anyone know the function of a simple ac generator?

transformers are basically very simple you just have to use the equation vs/vp=ns/np
voltage in the secondary coil divided by the primary coil = numbers of coils in secondary coil/ number of coils in primary coil.
so its basically a ratio thing
so if you're given a question for example that if you needed to step down 230,000 volts to 230v and you had 5000 turns on the secondary coil you would simply
go 230/230,000=1/1000
1/1000= ?/5000 so the awnser is you would need 5 turns in the primary coil.
and for other things you just rearrange the formula accordingly.
and basiclaly step up tranformers have less turns in the secondary coil than the primary coil and for step down transformers as in this example the number of turns in the secondary coil is higher than the number of turns in the primary coil
think the revision guide explains it clearer than me so have a look in cgp

Thanks

How does increasing the tube voltage give the electrons more kinetic energy? Is there an equation that links the two?

There is SO MUCH PHYSICS!
Dream question:

'Fail to calculate this really difficult capacitor question'

I HATE capacitors more than anything.