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AQA Physics PHYA5 - Thursday 18th June 2015 [Exam Discussion Thread]

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Explanation of how to convert from apparent magnitude to brightness? Its something to do with 2.5^x???

Apparent magnitude to intensity you mean? What sort of question have you seen that relates the two?

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Reply 2121

DannySmith420

Can anyone help me with June 2013 4(b)(iii) about gas

Reply 2122

aprocrastinator

any idea of definitions we need to know for section A? loads came up last year and I didn't know any of them haha

Reply 2123

ZedRigby

Original post by DannySmith420

Can anyone help me with June 2013 4(b)(iii) about gas

You just have to use n=PV/RT again but with the new values, then multiply n by the molar mass given to you in the previous question.

Reply 2124

slaven123

Original post by CD223

Apparent magnitude to intensity you mean? What sort of question have you seen that relates the two?

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No brightness. Question 2b(ii) on june 2010.
http://filestore.aqa.org.uk/subjects/AQA-PHYA5-2-A-W-QP-JUN10.PDF

Reply 2125

000alex

Original post by CD223

Apparent magnitude to intensity you mean? What sort of question have you seen that relates the two?

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How many times brighter one star is than another is 2.5^(delta m)
I asked before if we need to know this but nobody knows

Reply 2126

ZedRigby

Hey, would anyone be able to post how to derive the kinetic theory model as how they would want you write it in an answer? I just want to learn it so I can nail it if it comes up :smile:

Reply 2127

slaven123

Original post by 000alex

How many times brighter one star is that another is 2.5^(delta m)
I asked before if we need to know this but nobody knows

Ahh okay. They've asked about it before so I guess you do need to know it

Reply 2128

CD223

Original post by slaven123

No brightness. Question 2b(ii) on june 2010.
http://filestore.aqa.org.uk/subjects/AQA-PHYA5-2-A-W-QP-JUN10.PDF

All you need to know is that each magnitude difference represents a change of

100^{\frac{1}{5}}

.

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Reply 2129

CD223

Original post by 000alex

How many times brighter one star is than another is 2.5^(delta m)
I asked before if we need to know this but nobody knows

It's not exactly 2.5 - it's the fifth root of 100. Might sound stupid but when multiplying by large numbers it can give you the incorrect answer easily.

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Reply 2130

slaven123

Original post by CD223

All you need to know is that each magnitude difference represents a change of

100^{\frac{1}{5}}

.

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A change of what though? Intensity, brightness...?

Reply 2131

CD223

Original post by slaven123

A change of what though? Intensity, brightness...?

"Brightness". Although equally I've seen them use intensity just as much before.

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Reply 2132

000alex

Original post by CD223

It's not exactly 2.5 - it's the fifth root of 100. Might sound stupid but when multiplying by large numbers it can give you the incorrect answer easily.

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The markscheme only used 2.5 so idk

Reply 2133

CD223

Original post by 000alex

The markscheme only used 2.5 so idk

I'd just be careful. The mark schemes are so inconsistent.

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Reply 2134

slaven123

Original post by CD223

"Brightness". Although equally I've seen them use intensity just as much before.

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Ok, cheers. I think I get that now.

Reply 2135

gcsestuff

What does the first minimum in electron diffraction represent ?

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Reply 2136

EconFan_73

Does anyone know why during electron diffraction the deflection is purely down to diffraction and not the positively charged nuclei affecting the paths of the electrons?

Reply 2137

coqthepoliceman

does anyone have a list of all the keywords and their definitions that we need for nuclear&thermal section

Reply 2138

AR_95

Original post by coqthepoliceman

does anyone have a list of all the keywords and their definitions that we need for nuclear&thermal section

Try the book glossary lol?

Reply 2139

CD223

Original post by gcsestuff

What does the first minimum in electron diffraction represent ?

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Electrons behave like waves with a de Broglie wavelength - this minimum represents where destructive interference first takes place where beams superpose on top of one another (see unit 2 notes). All you need to know is that the first minimum is where