[Ari Ben Canaan]

So, just thought I'd create this thread for all us CIE students to discuss the exam after we've done it.

Just a note, you'll should not post up answers here to the exam paper until the very next day.

So how's everyone's revision going ?

[Zishi]

(Original post by Ari Ben Canaan)
So, just thought I'd create this thread for all us CIE students to discuss the exam after we've done it.

Just a note, you'll should not post up answers here to the exam paper until the very next day.

So how's everyone's revision going ?

Lol. I will try to avoid discussing it until my exams are over. Anyway, done with physics already, revising chemistry.

[Ari Ben Canaan]

(Original post by Zishi)
Lol. I will try to avoid discussing it until my exams are over. Anyway, done with physics already, revising chemistry.

Cool stuff. I'm just going through things one last time.

Just got to remain calm and composed now !

[Ari Ben Canaan]

(Original post by Zishi)
Lol. I will try to avoid discussing it until my exams are over. Anyway, done with physics already, revising chemistry.

You remember that question in May 2009 Paper 4 ?

Question 9.... Do you understand how they got the answer to the last part ?

[Zishi]

(Original post by Ari Ben Canaan)
You remember that question in May 2009 Paper 4 ?

Question 9.... Do you understand how they got the answer to the last part ?

Yeah, the 0.92 is N/No. No is 0.98 times 3.5x10^2 and N is 0.9 times 3.5x10^5. Do you get it?

[Ari Ben Canaan]

(Original post by Zishi)
Yeah, the 0.92 is N/No. No is 0.98 times 3.5x10^2 and N is 0.9 times 3.5x10^5. Do you get it?

No, unfortunately :/

[Zishi]

(Original post by Ari Ben Canaan)
No, unfortunately :/

It talks about the uncertainty. 2% means that during first time interval the 2% of the nuclei decay and 98% remain. That's why we multiply the initial number of nuclei by 0.98 to get the nuclei we have. And for the maximum uncertainty of 10%,the 10% of original nuclei should have decayed and so at that time we'll have 90% of the initial nuclei. That's how I have done it. Mark scheme changes it directly to 92% for further calculation.

[Ari Ben Canaan]

(Original post by Zishi)
It talks about the uncertainty. 2% means that during first time interval the 2% of the nuclei decay and 98% remain. That's why we multiply the initial number of nuclei by 0.98 to get the nuclei we have. And for the maximum uncertainty of 10%,the 10% of original nuclei should have decayed and so at that time we'll have 90% of the initial nuclei. That's how I have done it. Mark scheme changes it directly to 92% for further calculation.

But that's a 2% uncertainty how does it imply a decay of nuclei ?

[Zishi]

(Original post by Ari Ben Canaan)
But that's a 2% uncertainty how does it imply a decay of nuclei ?

It means that there will be an error of 2% while measuring the count rate. So to make allowance for the error, I have assumed that 2% of it decays during the first time interval. Anyway, I don't think that my way is perfect(although it does give the correct answer), so I think you should make a thread about it in physics help forum.

[bmqib]

Subbed

From what I remember I took the initial as 100, the final as 92, and plugged it in the formula

[Ari Ben Canaan]

(Original post by Zishi)
It means that there will be an error of 2% while measuring the count rate. So to make allowance for the error, I have assumed that 2% of it decays during the first time interval. Anyway, I don't think that my way is perfect(although it does give the correct answer), so I think you should make a thread about it in physics help forum.

Any idea why the amplitude of the information signal has to be less than half the amplitude of the carrier wave ?

[Zishi]

(Original post by Ari Ben Canaan)
Any idea why the amplitude of the information signal has to be less than half the amplitude of the carrier wave ?

As the course book says, "the variation in amplitude at top would be confused with the variation in amplitude at bottom of the wave". Too bad that it doesn't say much more about it.

[Zishi]

(Original post by Ari Ben Canaan)
Any idea why the amplitude of the information signal has to be less than half the amplitude of the carrier wave ?

What variant will you be giving? 41, 42 or 43?

[Ari Ben Canaan]

(Original post by Zishi)
What variant will you be giving? 41, 42 or 43?

42. You ?

[Zishi]

(Original post by Ari Ben Canaan)
42. You ?

Same.

[YaaahSarah]

Anyone doing IGCSE?

[Ari Ben Canaan]

(Original post by YaaahSarah)
Anyone doing IGCSE?

This is an A Level thread :P

I did my IGCSEs.

[bmqib]

mayn i'm getting 100 fo sho inshallah

[YaaahSarah]

(Original post by Ari Ben Canaan)
This is an A Level thread :P

I did my IGCSEs.

Ohh, sorry! *awkwardly exits*

[vishcr7]

can we discuss the answers for physcis 42 here?
and does anyone put up the paper with solutions here?