PHYA5 ~ 20th June 2013 ~ A2 Physics

x

Hey, it seems like you're really wised up about this, so I have a few questions to ask you if it's not too much trouble :smile:

Do we need to know what the Black-body radiation curves look like, as in do we need to be able to replicated them in some sort of way?

I don't really know what I'm doing regarding stellar spectroscopy, could you give me some pointers on those? Like the H Balmer series, I'm not really sure what they're for.

Evidence for the big bang?

Thanks!

Reply 1101

Lepton

9

Original post by crc290

Well at least now you can relax and not have to revise frantically last minute like me! :redface:

Good luck for the exam :smile:

I will never relax so long as I have an exam to come :tongue:

Thank you, good luck also! :smile:

Reply 1102

crc290

14

Original post by Thr33

Course I can :P

An Ionisation Chamber:

Chamber with air at 1 atm pressure, with a source outside the chamber. When radiation enters the chamber, it causes ionisation; and these ions are attracted to either one of the "electrodes" - either the wall of the chamber, or a central metal electrode placed within the chamber (these are connected in a circuit, with a basic cell, and a picoammeter in series). As such, the movement of ions means that there is a movement of electrons, so a current is generated (as seen on the ammeter). The current is proportional to the number of ions created per second. (So is higher for alpha than beta etc.)

A Cloud Chamber:

Supersaturated air at a very low chamber (eg with ethanol vapour). Ionisation in the air causes a track of condensed vapour - ionising particle causes the formation of droplets. Alpha particles produce straight tracks radiating from the source, all of the same length - because they are (relatively) heavy and all of the same energy.
Beta particles produce wispy tracks that are deflected by collisions with the air molecules. They're less ionising so they tracks are fainter, and they have varying lengths (as the ke of beta particles varies).

Enjoy!

Please tell me this is just for OCR or something. This thread is confusing me :s-smilie:

Reply 1103

iCiaran

11

Original post by crc290

Please tell me this is just for OCR or something. This thread is confusing me :s-smilie:

Also never seen this before :/

Reply 1104

Thr33

Original post by kingm

I don't think this can come up (to the extent that you've described). See above but i'm pretty sure those experiments are in the book to help you gage the characteristics of the 3 types of radiation. They may, for example, tell you something about the experiment and then get you to compare the 3 types or something like that.

Yeah, i more or less agree (see my earlier post), but they might reference it, and it's worth knowing.

Reply 1105

crc290

14

Original post by iCiaran

Also never seen this before :/

Ah, are you doing AQA too?

Reply 1106

igloo1

Original post by Rorschace

Can someone explain how I can find "d" using the formula m-M=log(d/10) in Astrophysics..I forgot how to use log functions :frown:

e^(m-M) = d/10
e^(m-M) *10 = d

that should work..

Reply 1107

D4rth

9

Original post by Thr33

Course I can :P

An Ionisation Chamber:

Chamber with air at 1 atm pressure, with a source outside the chamber. When radiation enters the chamber, it causes ionisation; and these ions are attracted to either one of the "electrodes" - either the wall of the chamber, or a central metal electrode placed within the chamber (these are connected in a circuit, with a basic cell, and a picoammeter in series). As such, the movement of ions means that there is a movement of electrons, so a current is generated (as seen on the ammeter). The current is proportional to the number of ions created per second. (So is higher for alpha than beta etc.)

A Cloud Chamber:

Supersaturated air at a very low chamber (eg with ethanol vapour). Ionisation in the air causes a track of condensed vapour - ionising particle causes the formation of droplets. Alpha particles produce straight tracks radiating from the source, all of the same length - because they are (relatively) heavy and all of the same energy.
Beta particles produce wispy tracks that are deflected by collisions with the air molecules. They're less ionising so they tracks are fainter, and they have varying lengths (as the ke of beta particles varies).

Enjoy!

Thank you but I can't find those experiments on the specification nor did our teacher tell us about it so I don't think its something we need to know, or go into that much detail.

Posted from TSR Mobile

Reply 1108

igloo1

Original post by crc290

Please tell me this is just for OCR or something. This thread is confusing me :s-smilie:

Think AQA only need to know the cloud chamber one.

Reply 1109

bugsuper

8

All of those experiments are in the Nelson Thornes textbook, and they might be used as part of a question, but I don't think there'll be a six marker like "explain the inversion tube experiment"

still, kids, it's always worth flexing your short-term memory... never know what's going to come up with AQA

Reply 1110

MatLH

Original post by igloo1

e^(m-M) = d/10
e^(m-M) *10 = d

that should work..

Use 10 as the base unit- The formula doesn't use natural logarithms

Reply 1111

crc290

14

Original post by igloo1

Think AQA only need to know the cloud chamber one.

Nooo, don't say that. I know neither :s-smilie:

Reply 1112

Thr33

Original post by Anythingoo1

Hey, it seems like you're really wised up about this, so I have a few questions to ask you if it's not too much trouble :smile:

Do we need to know what the Black-body radiation curves look like, as in do we need to be able to replicated them in some sort of way?

I don't really know what I'm doing regarding stellar spectroscopy, could you give me some pointers on those? Like the H Balmer series, I'm not really sure what they're for.

Evidence for the big bang?

Thanks!

Big bang I need to look over tonight, so I'm not of much use atm.

Black body radiation - just know the rough shape, and what happens if you have a black body at a greater temperature (shift towards UV). It's worth knowing as well as it explains why hotter stars aren't as bright (visible) as they are powerful (em radiation) - due to a large amount of radiation being in the UV spec.

Stellar spectroscopy - there's a pathetically wonderful mnemonic - "Oh be a fine girl, kiss me" (Yep...)
The only way to really get the hang of those is to learn them - there's not much else too it.
Balmer series - this relates to spectral classes - which absorption lines are with which spectra are in the spec too. Just gotta learn them. The existence of the lines themselves is due to elements in the atmosphere of the star which absorb specific frequencies (remember E=hf?) for excitation. When they de-excite, the radiation goes in all directions - not the initial direction, so the intensity is less. You only get H lines for stars which are hot enough for the electrons to be in the n=2 state - again, easiest way to learn it is from the spec/CGP rev guide.

Reply 1113

Thr33

Original post by D4rth

Thank you but I can't find those experiments on the specification nor did our teacher tell us about it so I don't think its something we need to know, or go into that much detail.

Posted from TSR Mobile

They're in the list of core practicals. Don't worry about them excessively, but know roughly how they work. AQA pull out competely and utterly random questions from time to time, so it's best to prepare for the worst.

Reply 1114

Serpentine111

12

Why are there no January ones for this unit? :s-smilie:

Reply 1115

bugsuper

8

Original post by crc290

Just checked and there is no mention of cloud chambers or inversion tubes in the Nelson Thornes book at all. There is only a very brief section on ionisation chambers...

Wait, never mind. Found cloud chambers :redface:

The inversion tube experiment is defined in the chapter on specific heat capacity, but it's really simple

you get a tube of known length, and a known mass of the substance whose specific heat capacity you want to test. mgl = the change in gravitational potential energy when the substance falls from one end of the tube to the other. You turn it over about 50 times, so 50mgl is the total change in gpe; then you assume that all of this was converted into thermal energy (when the substance hit the bottom of the tube), measure its temperature change, and hey presto, you can calculate specific heat capacity

Reply 1116

laurenb11

Dreading tomorrow morning...

Reply 1117

anuradha_d

1

Hey - six marker predictions? (Astro and Core) also im worried about the lack of explanation about Carbon Dating (or i may not have read it properly :P)