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Physics, Chemistry and Biology: Post your doubts here!

S

shazmina

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salma_69 said:
it's C...:p
Click to expand...

yea i ws about to tl ya de answer was C nd u wrote it...:)
Now in dis case u c dey havnt mntnd us nething bt de unstable nuclei r sumthing lk dat soooo wat i did ws
fr example i took 2 nd assumed it to be one going on a decay....so 1/16 of 2 is gonna be 1/8 so dis 1/8 falls on de 4 times de decay...ie 2/2= 1
1/2=0.5
0.5/2=0.25
0.25/2=0.125 which is 1/8
therefore it fall on de 4th decay..i hope u gt until dis...den de nxt step is gonna b simple...we knw dat the time fr a half life of a substance is fixed so goes like dis 4 into 6000 which is 24000..hope u gt it....
 
salma_69

salma_69

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shazmina said:
yea i ws about to tl ya de answer was C nd u wrote it...:)
Now in dis case u c dey havnt mntnd us nething bt de unstable nuclei r sumthing lk dat soooo wat i did ws
fr example i took 2 nd assumed it to be one going on a decay....so 1/16 of 2 is gonna be 1/8 so dis 1/8 falls on de 4 times de decay...ie 2/2= 1
1/2=0.5
0.5/2=0.25
0.25/2=0.125 which is 1/8
therefore it fall on de 4th decay..i hope u gt until dis...den de nxt step is gonna b simple...we knw dat the time fr a half life of a substance is fixed so goes like dis 4 into 6000 which is 24000..hope u gt it....
Click to expand...

thnx aloooooooooooooooooot.....:ROFLMAO:
 
omaaaar

omaaaar

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shazmina said:
yea i ws about to tl ya de answer was C nd u wrote it...:)
Now in dis case u c dey havnt mntnd us nething bt de unstable nuclei r sumthing lk dat soooo wat i did ws
fr example i took 2 nd assumed it to be one going on a decay....so 1/16 of 2 is gonna be 1/8 so dis 1/8 falls on de 4 times de decay...ie 2/2= 1
1/2=0.5
0.5/2=0.25
0.25/2=0.125 which is 1/8
therefore it fall on de 4th decay..i hope u gt until dis...den de nxt step is gonna b simple...we knw dat the time fr a half life of a substance is fixed so goes like dis 4 into 6000 which is 24000..hope u gt it....
Click to expand...
I didnot understand the method so could you please explain in easy words
 
Iridescent

Iridescent

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omaaaar said:
http://papers.xtremepapers.com/CIE/Cambridge IGCSE/Physics (0625)/0625_s05_qp_1.pdf
Question 29 answer is D ,not C why
And Question 32 answer is B ,not A why
Click to expand...

Q29: Because voltmeter is always connected parallel to the device. In C, it is connected parallel to the lamp but it doesnot measure the voltage across the lamp due to the presence of the resistor that alters the voltage measured.
Q31: By moving the contact, the voltage is varied. A is also a variable resistor but for varying the boltage across any component, B is used.
 
omaaaar

omaaaar

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Iridescent said:
Q29: Because voltmeter is always connected parallel to the device. In C, it is connected parallel to the lamp but it doesnot measure the voltage across the lamp due to the presence of the resistor that alters the voltage measured.
Q31: By moving the contact, the voltage is varied. A is also a variable resistor but for varying the boltage across any component, B is used.
Click to expand...

Thanks for the explaination
 
$$AK$$

$$AK$$

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hey,
can you please help me in physics(o625)/summer 2000/paper 1 in these questions:
Q6
Q11
Q33
Thnx
:D
 
O

Othman

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omaaaar said:
http://papers.xtremepapers.com/CIE/Cambridge IGCSE/Physics (0625)/0625_w05_qp_1.pdf
Question 21 the answer is A could you explain it in detail
And Question 39 of the same paper that why the number of neutrons becomes less
Click to expand...
For Q21, the answer is A because the angle of refraction is bigger than the incidence as it is from glass to air. Also it is not totally refracted some is reflected.
It's not B because the angle of incidence is less than the critical angle.
It's not C because speed of light is faster in air so the refraction angle must be larger as I said earlier.
It's not D because there is nothing like that ( In our syllabus at least ).

For 39 I had the same doubt about it so I asked about it, the electron that the sample releases on decay is actually a neutron which is negatively charged so a neutron is lost.
 
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