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Edexcel Physics Unit 2 "Physics at work" June 2013 Watch

  • View Poll Results: The last question - Does resistance increase or decrease?
    It increases ( using V=IR or some other method)
    70.73%
    It decreases using the 'lattice vibrations' theory
    29.27%

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    guys what is a critical angle ? :O
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    (Original post by x0x)
    I said that I decreases
    so for a given voltage the resistance should increase
    since V=IR
    but its true ... when current decreases there is less heating but I depended on the equation since there were 4 marks and in mark schemes they almost always require you to quote a relevant equation :P
    Considering it was a 4 mark question, I think a very long explanation should be given e.g. 671 post
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    Estimated grade boundary for an A?

    Thanks.
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    (Original post by Freddy-Francis)
    guys what is a critical angle ? :O
    Angle of incidence at which angle of refraction=90*, so light travels along medium boundary.
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    what did u guys put for the "Explain why the following observations may be understood by using a photon model of light, rather than a wave model"?
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    What did everyone say for the q on stating EM radiation for the since plate photoelectric effect q?

    I put UV for two reasons. If you know from experience UV radiation and visible light appear to be associated most with zinc. Also there was a q on radio waves frequency from before like the start of the paper, which was a small hint, from that I realised that this unknown radiation is above both visible light and radio waves in terms of frequency, so it's either UV, X-ray, gamma. Due to first reason I put down UV, I have more faith in it.
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    (Original post by krisshP)
    Estimated grade boundary for an A?

    Thanks.
    im thinking 58-59
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    (Original post by krisshP)
    What did everyone say for the q on stating EM radiation for the since plate photoelectric effect q?

    I put UV for two reasons. If you know from experience UV radiation and visible light appear to be associated most with zinc. Also there was a q on radio waves frequency from before like the start of the paper, which was a small hint, from that I realised that this unknown radiation is above both visible light and radio waves in terms of frequency, so it's either UV, X-ray, gamma. Due to first reason I put down UV, I have more faith in it.
    its UV since frequency was 1.04x10^15 or something and i memorized the wavelengths and this one ws 2.somethingx10^-7 which is UV
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    (Original post by Freddy-Francis)
    what did u guys put for the "Explain why the following observations may be understood by using a photon model of light, rather than a wave model"?
    It was a QWC question worth 5 marks I thin. I ended up just stating stuff like
    One photon releases one electron
    E=hf
    Wave energy depends on frequency for particle model an on intensity for wave model
    Energy supply is continuous, so can build up for wave model
    ....
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    (Original post by hamzeh h)
    its UV since frequency was 1.04x10^15 or something and i memorized the wavelengths and this one ws 2.somethingx10^-7 which is UV
    it didnt ask for specific..
    It just said which part.
    So i put the high end :eek:
    And put examples like xrays, gamma rays :O
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    (Original post by Freddy-Francis)
    what did u guys put for the "Explain why the following observations may be understood by using a photon model of light, rather than a wave model"?
    its repeated in many pastpapers just expain about one photon giving energy to one electron and frequency being propoptional to energy..etc and that if it was a wave keeping the light shone will accumulate energy and electrons will be emitted but doesnt happen and talk about threshold frequency
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    (Original post by Freddy-Francis)
    it didnt ask for specific..
    It just said which part.
    So i put the high end :eek:
    And put examples like xrays, gamma rays :O
    well Ultra-violet is a part of electromagnetic spectrum :P
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    (Original post by krisshP)
    It was a QWC question worth 5 marks I thin. I ended up just stating stuff like
    One photon releases one electron
    E=hf
    Wave energy depends on frequency for particle model an on intensity for wave model
    Energy supply is continuous, so can build up for wave model
    ....
    i put the similar as u.
    I also put that the number of photoelectrons emitted per second is proportional to the intensity of radiation. <<any marks/
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    (Original post by hamzeh h)
    its UV since frequency was 1.04x10^15 or something and i memorized the wavelengths and this one ws 2.somethingx10^-7 which is UV
    The radio waves v=flambda question on section b was a nice hint helping for this question, I'm surprised nobody made use of it.
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    (Original post by krisshP)
    The radio waves v=flambda question on section b was a nice hint helping for this question, I'm surprised nobody made use of it.
    yaa
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    (Original post by hamzeh h)
    yaa
    Did you do that as well? Look at post 685, that's how I figure it out. They expected you to be so cunning.
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    qu6) the transition which did u guys choose? 5 to 4?
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    (Original post by Freddy-Francis)
    qu6) the transition which did u guys choose? 5 to 4?
    4 to 5 it was absorption of lowest frequency
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    Grade boundries estimates for the A guys?
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    (Original post by Freddy-Francis)
    qu6) the transition which did u guys choose? 5 to 4?
    I did 4 to 5 beacuse it was being absorbed
 
 
 
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