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PHYA5 ~ 20th June 2013 ~ A2 Physics

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Is there a chance a six marker might come up on something to do with the thermal side of this unit? I really hope not...

Reply 1241

ThatRandomGuy

Original post by Jack93o

mass is always less than it was before for fission and fusion

So for fission the new nuclei have less mass than the original?

Reply 1242

c.j.w

Original post by D4rth

Are you sure about the data sheet? It might be outdated. The newest data sheet says 931.3

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Maybe it is then, I'm sure the one I'm given in the exam is the same, but I wouldn't put it past my school to give me the wrong one. I'll just use 931.3 then to be sure, thanks! :smile:

Reply 1243

Thr33

Original post by ThatRandomGuy

So for fission the new nuclei have less mass than the original?

Yes. Hence you get energy out. E = mc^2 and all that.

Reply 1244

bebubebubebu

Original post by Science211

Help on June 12 part A 3)c) anyone? I'm stuck??

http://filestore.aqa.org.uk/subjects/AQA-PHYA5-1-QP-JUN12.PDF
http://filestore.aqa.org.uk/subjects/AQA-PHYA52A-W-MS-JUN12.PDF

http://www.cyberphysics.co.uk/Q&A/KS5/radioactivity/Q13.html

Reply 1245

UnknownOrigin

Original post by Jack93o

they would never go something that specific for a 6 marker (i hope)

Maybe.

Or: explain how a CCD works and explain its advantages over photographic film

Reply 1246

sports_crazy

Original post by Jack93o

mass is always less than it was before for fission and fusion

yeah, increase in binding energy leads to decrease in mass

How can fusion result in decrease in mass. I am confused :s-smilie:

. Wont it increase like from 2 hydrogen to helium.

(edited 10 years ago)

Reply 1247

Jack93o

Original post by ThatRandomGuy

So for fission the new nuclei have less mass than the original?

yeah

Reply 1248

Jack93o

Original post by UnknownOrigin

Maybe.

Or: explain how a CCD works and explain its advantages over photographic film

what sort of advanatges are there over photographic film?

I know about the massively increased quantum efficiency with CCD, but what else?

I'd be ****ed if that question came up

Reply 1249

TeddyBasherz

Original post by UnknownOrigin

Maybe.

Or: explain how a CCD works and explain its advantages over photographic film

Is the advantage that, for a CCD, the quantum efficiency is much greater than that for photographic film, which is around 4% compared to a CCD with 70-80%?

Reply 1250

anuradha_d

Hey everyone

I dont understand how question 3 in June 2012 was answered... any help please?

Reply 1251

TeddyBasherz

Original post by sports_crazy

How can fusion result in decrease in mass. I am confused :s-smilie:

. Wont it increase like from 2 hydrogen to helium.

As in there is a mass defect. The total mass of the two old nuclei combined will be slightly more than the larger, more stable nucleus created. This change in mass leads to energy given out to the surroundings (equivalent to E=(delta)mc^2).

Reply 1252

laser174572

Anyone doing turning points know whether the tip of an STM is positively or negatively charged? The textbook says negatively but I'm not convinced because surely it has to be positively charged so as it attracts the tunnelling electrons?

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Reply 1253

Jack93o

Original post by sports_crazy

How can fusion result in decrease in mass. I am confused :s-smilie:

. Wont it increase like from 2 hydrogen to helium.

what I meant, is that the combined nucleus would have less mass than the two individual nuclei which were fused together

e.g.

each of those nuclei has a mass of 1kg

now, you'd expect the combined nucleus to be 2kg (1kg + 1kg)

BUT that doesn't actually happens

the combined nucleus would lose some of the mass, leaving it with say 1.9kg

the reason it loses mass, is because the nucleons (protons and neutrons) in the two nuclei lose potential energy

energy = mc^2

so if you lose energy, you also lose mass

apparently the same effect can be seen with boiled water, if you weigh a cup of 100 degree Celsius water, it would weigh more than the same cup of water at room temperature for example (but the difference in mass is very very slim)

Reply 1254

Jack93o

Original post by TeddyBasherz

Is the advantage that, for a CCD, the quantum efficiency is much greater than that for photographic film, which is around 4% compared to a CCD with 70-80%?

thats the only thing I could think of, maybe you could add that CCD is digital, so it could be more readily used for data analysis or some crap like that, but yeah, thats a nasty question

Reply 1255

posthumus

Original post by laser174572

Probably negatively charged due to the electrons.... the electrons are accelerated via a positive anode in an electric gun and then this accelerates through the microscope

Reply 1256

bebubebubebu

Original post by anuradha_d

Hey everyone

I dont understand how question 3 in June 2012 was answered... any help please?

read this, it really helps me
http://www.cyberphysics.co.uk/Q&A/KS5/radioactivity/Q13.html

Reply 1257

laser174572

Original post by posthumus

Probably negatively charged due to the electrons.... the electrons are accelerated via a positive anode in an electric gun and then this accelerates through the microscope

Don't the electrons quantum tunnel from the sample to the tip? I thought the one with an electron gun was transmission electron microscopy, not scanning?

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Reply 1258

posthumus

Original post by laser174572

Don't the electrons quantum tunnel from the sample to the tip? I thought the one with an electron gun was transmission electron microscopy, not scanning?

Posted from TSR Mobile

Okay sorry don't listen to me :colondollar:

I still need to read this stuff... I'm only assuming! :redface:

& there's turning points thread here I made: http://www.thestudentroom.co.uk/showthread.php?t=2382437&page=4

Just easier to get to people who have turning points related questions

Reply 1259

UnknownOrigin

Original post by Jack93o

what sort of advanatges are there over photographic film?

I know about the massively increased quantum efficiency with CCD, but what else?

I'd be ****ed if that question came up

-Increased quantum efficiency
-Its digital - so it can be easily processed by computers/programmes
-Can detect wavelengths beyond visible light region - so astronomers benefit as they can explore more