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

Original post by Mehrdad jafari

It really depends on how well you the content. Also you need to be very familiar with exam papers and techniques. But what i simply meant was that if you think it is possible then it's possible. You should be so confident that you shouldn't be asking this

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Lol well, I haven't read the book or done a single paper yet. Let's see how it goes

Reply 1902

Original post by ubisoft

Lol well, I haven't read the book or done a single paper yet. Let's see how it goes

Neither have i. Just have confidence and don't stress out, that's it

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Reply 1903

Original post by Mehrdad jafari

Neither have i. Just have confidence and don't stress out, that's it

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I did, but I kind of lost it today after FP2. Don't think I'll get my firm offer, so losing motivation a bit.

Reply 1904

Is the decay constant the same of same isotopes? and does it stay the same during decay?

Reply 1905

Original post by ubisoft

I did, but I kind of lost it today after FP2. Don't think I'll get my firm offer, so losing motivation a bit.

I do understand you man. It's a very intense moment when you think you are loosing something. But trust me you can still compensate. Also if your interview went well then there is also a chance that you will be accepted even if you think you don't get the place. But you don't want to perform well because you hold an offer, do you? Just stay focused and realise that it's just a moment that makes a difference

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Reply 1906

Original post by ubisoft

Is the decay constant the same of same isotopes? and does it stay the same during decay?

No because some isotopes are more likely to decay than others so they will have a greater decay constant. Decay constant is the same throughout the decay process, it's the activity that's decreasing as time goes by because the number of nucleus remaining to decay decreases, if that helps

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Reply 1907

Original post by Mehrdad jafari

No because some isotopes are more likely to decay than others so they will have a greater decay constant. Decay constant is the same throughout the decay process, it's the activity that's decreasing as time goes by because the number of nucleus remaining to decay decreases, if that helps

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Yeah but I said same isotopes? All same isotopes have same decay constant?

Reply 1908

Original post by ubisoft

Yeah but I said same isotopes? All same isotopes have same decay constant?

I wouldn't think so, that's why they are isotopes. For example uranium in power stations is a unique isotope of uranium( forgot the Ar) because it has a greater decay constant if I'm not mistaken

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Reply 1909

dannyoboy007

11

How do I solve these sorts of questions?

Reply 1910

Fvthoms

ImageUploadedByTapatalk1434518796.026032.jpg

ImageUploadedByTapatalk1434518806.904882.jpg

What is the criteria for deciding whether a lens will be the eyepiece or objective on a refracting telescope?

Reply 1911

frankiejayx

Is magnification Beta / Alpha ?

Also is it only mirrors that suffer from spherical abberation??

(edited 8 years ago)

Reply 1912

_Caz_

10

Original post by Fvthoms

What is the criteria for deciding whether a lens will be the eyepiece or objective on a refracting telescope?

Is this the one where the lens is like 40cm or something? (I think I remember doing this question)

If so it would be the objective lens. In refracting telescopes the focal length of the eyepiece lens is only about 2cm. If it was 40cm, the focal length of the refracting telescopes objective lens would have to be huge to have such a big eyepiece lens focus length. And we know that refracting telescopes are not great when they're large, the get too heavy and awkward to move, the lenses distort etc.

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Reply 1913

JJBinn

Original post by CD223

Because that's the temperature that the mould decreases to, from its initial temperature of 327 degrees.

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How do you know that? It says the molten lead starts at 327 and the iron finishes at 84. I don't understand why you can deduce that the final temperature is therefore 327-84? It's probably really basic just don't see it :s-smilie:

Reply 1914

Fvthoms

[QUOTE=_Caz_;57110427]
X

Thanks Caz; I think me and you have the same exam timetable by the way...

Reply 1915

_Caz_

10

Original post by Fvthoms

Thanks Caz; I think me and you have the same exam timetable by the way...

I kinda noticed you keep popping up everywhere haha! Have you got fp2 on Monday as well?

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Reply 1916

CD223

OP

10

Original post by Me123456789

Oh, that makes more sense now, thanks :thumbsup:

No problem!

Original post by dannyoboy007

How do I solve these sorts of questions?

The ratio of number of photons incident on the detector to the number of photons produced by the source is equal to the ratio of their two surface areas.

Original post by frankiejayx

Is magnification Beta / Alpha ?

Also is it only mirrors that suffer from spherical abberation??

Yeah magnification can be expressed as:

• Image height divided by object height
• Image distance divided by object distance
• Angle subtended by the image to the eyepiece lens divided by the angle subtended by the object to the unaided eye (beta over alpha!)

Reflecting telescopes are the only ones to suffer from spherical aberration but this can be solved by using a parabolic mirror.

Original post by JJBinn

How do you know that? It says the molten lead starts at 327 and the iron finishes at 84. I don't understand why you can deduce that the final temperature is therefore 327-84? It's probably really basic just don't see it :s-smilie:

It says that they reach thermal equilibrium meaning they end up at the same temperature and there's no net transfer of heat energy between them. As such, the final temperature of the molten lead (which is now solid) is 84 degrees as this is the same as the final temperature of the iron mould.

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Reply 1917

JJBinn