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Author Topic: Edexcel PHYSICS Doubts  (Read 202824 times)

Offline Banana

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Re: Edexcel PHYSICS Doubts
« Reply #630 on: June 04, 2011, 03:43:30 pm »
Quote from: ang3l on June 04, 2011, 03:23:21 pm
Sorry for being dumb..But why 1 cm ? Is it 'cause the line is t + 3/4 T  ???

And thx alot :)

Look....u measure the distance between 2 compressions and multiply by three quarters....thats wat GG meant  ;)....then u measure out that distance from the compression points and just PLOT it  :P
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Offline Malak

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Re: Edexcel PHYSICS Doubts
« Reply #631 on: June 04, 2011, 03:49:13 pm »
Okay k Thanks  ::)
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Offline Banana

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Re: Edexcel PHYSICS Doubts
« Reply #632 on: June 04, 2011, 04:20:54 pm »
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Offline Banana

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Re: Edexcel PHYSICS Doubts
« Reply #633 on: June 04, 2011, 04:40:37 pm »
Somebody pls help me out with this question.....im totally confused  :-\:

Why does the Kinetic E of emitted electrons in the photoelectric effect depend only on the frequency and not on the intensity of the light????
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Offline Malak

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Re: Edexcel PHYSICS Doubts
« Reply #634 on: June 04, 2011, 05:23:52 pm »
^ Because its the frequency of the light that determines the photon energy (E=hf), A brighter light i.e. greater intensity only means that there are more photons present so more electrons can be emitted. It doesnt effect the K.E of the electrons.
More energy means more K.E
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Offline The Golden Girl =D

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Re: Edexcel PHYSICS Doubts
« Reply #635 on: June 04, 2011, 05:25:42 pm »
Quote from: MujtabaM on June 04, 2011, 04:40:37 pm
Somebody pls help me out with this question.....im totally confused  :-\:

Why does the Kinetic E of emitted electrons in the photoelectric effect depend only on the frequency and not on the intensity of the light????

It is due to the equation E = hf ...

h is Planck's constant ,and since it's constant this means there is a relation between Energy and frequency .

And from this equation we got to know that the Energy of a Photon depends on frequency


I don't think we should know WHY exactly it is this way ...I'm not  sure if you we need to know it or not , but I hope you got my point :)
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Offline Banana

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Re: Edexcel PHYSICS Doubts
« Reply #636 on: June 04, 2011, 05:56:36 pm »
Thank you very much Ang3l and GG....the fog in my head is clearin'  :)
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Offline The Golden Girl =D

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Re: Edexcel PHYSICS Doubts
« Reply #637 on: June 04, 2011, 06:12:31 pm »
You're welcome :)
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Offline Romeesa-Chan

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Re: Edexcel PHYSICS Doubts
« Reply #638 on: June 04, 2011, 07:46:43 pm »
Physics 6B, Sample Paper:

*Q1bii- where did 8 come from ? :S

*Q2ciii- No idea what the marking scheme says!

*Q3 a & b

*Q4 a & dii

Link: http://www.edexcel.com/migrationdocuments/GCE%20New%20GCE/Physics-Practical-Alternative-SAMs.pdf

Please help me. Have exam the next day (Monday)!!!
« Last Edit: June 04, 2011, 08:53:19 pm by Romeesa-Chan »
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elemis

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Re: Edexcel PHYSICS Doubts
« Reply #639 on: June 05, 2011, 05:42:25 am »
Q1

% Uncertainty = uncertainty of instrument / actual measurement.

Each foil is 15 micrometres thick. When you decide to measure the thickness of the foil will you measure the thickness of only one foil or several ?

You would do it for several so as to gain an average and eliminate random uncertainties.

If I were you I would measure the thickness of 8 sheets or more. That's where the eight comes from.

Q2

In a roundabout fashion they are asking you to calculate the percentage uncertainty whilst showing workings.
« Last Edit: June 05, 2011, 05:45:58 am by Ari Ben Canaan »
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Offline Romeesa-Chan

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Re: Edexcel PHYSICS Doubts
« Reply #640 on: June 05, 2011, 11:21:51 am »
Quote from: Ari Ben Canaan on June 05, 2011, 05:42:25 am
Q1

% Uncertainty = uncertainty of instrument / actual measurement.

Each foil is 15 micrometres thick. When you decide to measure the thickness of the foil will you measure the thickness of only one foil or several ?

You would do it for several so as to gain an average and eliminate random uncertainties.

If I were you I would measure the thickness of 8 sheets or more. That's where the eight comes from.

Q2

In a roundabout fashion they are asking you to calculate the percentage uncertainty whilst showing workings.

For Q1. Why 8? It can be any number, right? Like. . . 10/12?

Can you please help with Q. 3 & 4?
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Offline Romeesa-Chan

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Re: Edexcel PHYSICS Doubts
« Reply #641 on: June 05, 2011, 11:31:37 am »
Momentum conservation using a linear air track.

Describe means of stopping the riders gently at the far end of the track.
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Offline deadlyelder

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Re: Edexcel PHYSICS Doubts
« Reply #642 on: June 05, 2011, 02:24:16 pm »
How to calclulate the Critical Angle? If anyone has example please post it for clarification I am confused.
Thanx
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Offline The Golden Girl =D

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Re: Edexcel PHYSICS Doubts
« Reply #643 on: June 05, 2011, 02:27:40 pm »
Quote from: deadlyelder on June 05, 2011, 02:24:16 pm
How to calclulate the Critical Angle? If anyone has example please post it for clarification I am confused.
Thanx

If a ray of light is moving from Denser *glass* to rarer *air*  then we use this formula

sin c= na / na

so Critical angle equals to sin inverse the refractive index of Air over the refractive index of Glass

i.e.

c = sin-1 [ na/ na ]




Example

c = sin-1 [ 1.00 / 1.5  ]
          = 42

I believe it's 42 :)

I hope you got it :D
« Last Edit: June 05, 2011, 02:29:36 pm by The Golden Girl »
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Offline MasterMath

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Re: Edexcel PHYSICS Doubts
« Reply #644 on: June 05, 2011, 02:40:43 pm »
I just want to make sure of something correct me if im wrong
In the photo electric effect .. when your shinning radiation on a metal's surface. If you increase the intensity you increase the number of electrons getting knocked out, but if you increase the frequency your just increasing the K.E the electrons gain right? So frequency has no effect on the current(number of electrons emitted)?
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