# OCR Physics A G485 - Frontiers of Physics - 18th June 2015Watch

3 years ago
#1301
relative sizes of atom and nucleus?
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3 years ago
#1302
(Original post by Jim997)
Used to determine the masses of charged ions and their relative abundances.

- A uniform magnetic field is used to deflect the charged ions in a circular path in an evacuatedchamber.

- A moveable detector used to find the radius of the path and the relative abundance of the ions.

- The radius r of the path in the magnetic field region is 𝑟 =𝑚𝑣/𝐵𝑄.

- The radius that the particle moves in (and hence the place where it hits the sensor) depends on thedifferent mass to charge ratio.
0
3 years ago
#1303
so frickin scared
0
3 years ago
#1304
(Original post by kate8)
relative sizes of atom and nucleus?
Nucleus is ~1/10,000th of the atom.
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3 years ago
#1305
(Original post by I Persia I)
Nucleus is ~1/10,000th of the atom.
atom is 10^-10m
nucleus is 10^-14m
proton/neutron is 10^-15m
electron < 10^-18m
1
3 years ago
#1306
When you have both and electric field and magnetic field, how do you work out the direction of movement of an electron in both fields?
0
3 years ago
#1307
(Original post by nothepreacher)
Ions travel through a velocity selector, where E and B can be controlled, so that ions passing straight into another magnetic field region B2 have a velocity E/B. The radius of the circular motion is mE/B1B2q. Once r is determined, the mass to charge ratio of the ions can be determined. I am not too sure actually. Can someone correct me?
where did you get mE/B1B2q from?
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3 years ago
#1308
(Original post by randomuser1)
Just did a past paper which included having to work out the momentum of an electron with a wavelength.E = hc/lambda also comes up when pair production occurs.
Yeah I meant when referring to waves etc. it will only be the quantum physics chapters. Nothing more like interference etc. Just the standard equations
0
3 years ago
#1309
(Original post by ETRC)
where did you get mE/B1B2q from?
pretty sure its in the textbook, ive seen it and have it written down
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3 years ago
#1310
(Original post by ETRC)
where did you get mE/B1B2q from?
B1 is the field in velocity selector where there is also E. So v=E/B1. In the second magnetic field region, the force on the ion is B2qv. Equate this to mv^2/r. But v can be expressed in terms of the field strengths as mentioned.
0
3 years ago
#1311
Has anyone got the 2014 paper?!
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3 years ago
#1312
i forgot mass spectrometer existed ffs more stuff to go over
0
3 years ago
#1313
(Original post by ETRC)
where did you get mE/B1B2q from?
http://www.st-ambrosecollege.org.uk/...Fields%20b.pdf
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3 years ago
#1314
(Original post by JB199612)
Has anyone got the 2015 paper?!
Lol we wish!
0
3 years ago
#1315
(Original post by ETRC)
i forgot mass spectrometer existed ffs more stuff to go over
Got plenty of time dw!
0
3 years ago
#1316
(Original post by coder4)
When you have both and electric field and magnetic field, how do you work out the direction of movement of an electron in both fields?
If the fields are acting in opposite directions to each other:

When E > B, the path of the ions will curve in the direction of the electric field.
When B > E, the path of the ions will curve opposite to the direction of the electric field.
When E = B, the ions will move in a straight path.
1
3 years ago
#1317
yeah my bad, i meant does anyone has the 2014 paper?!
0
3 years ago
#1318
(Original post by jcwh97)
Yeah I meant when referring to waves etc. it will only be the quantum physics chapters. Nothing more like interference etc. Just the standard equations
So I shouldn't waste my time going through diffraction patterns or interference right now?
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3 years ago
#1319
(Original post by nothepreacher)
Got plenty of time dw!
dw just went over it now- it's pretty simple
i'm better at maths than explanations so this was fine
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3 years ago
#1320
A few exam style questions on specific topic in link below. OCR is at the bottom, if anyone wants to do more questions.

http://www.physicsandmathstutor.com/...it-5-by-topic/
0
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