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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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    (Original post by LegendX)
    someone must know how to do this question? Click on the original post link to see the question. Someone? Anyone?
    Reason why I ask is I posted it earlier in the thread and it was overlooked also ^_^, must be really simple

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    (Original post by lucilleJR)
    could someone please explain to me why the answer to this question is A? thank you


    ignore this I've just realised it's on this thread
    I've seen this question too many times now. Just remember, V is constant so as a result if V = IR then V/I = R but if V is a constant, it would give you a graph in the form of 1/X = R and a 1/ X graph is a reciprocal graph so it looks like the graph in A.
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    For a standing wave on a wire, in the formulae L=nlambda/2, does L stand for length of wire, n for number of loops, lambda for standing wave wavelength?
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    (Original post by krisshP)
    For a standing wave on a wire, in the formulae L=nlambda/2, does L stand for length of wire, n for number of loops, lambda for standing wave wavelength?
    Yeah.
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    http://www.walter-fendt.de/ph14e/stwaverefl.htm

    everyone see this. It makes the topic standing waves make sense
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    http://www.edexcel.com/migrationdocu...e_20120525.pdf

    Ok guys a little help with 15 c) please?

    ' The smallest detail that can be seen on the image is half the length of the ultrasound
    pulse. The thumbnail on the fetus is 0.50 mm thick. The speed of ultrasound in the
    thumbnail is 2000 m s–1
    .
    Calculate the maximum pulse duration if the thumbnail is to be seen on the image'

    What does it mean by pulse length, and how is that different to pulse duration? And how do we go about solving this problem?

    Thanks a lot
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    does anyone on here know how to measure the rotation of the plan of polarisation and could explain to me please
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    (Original post by GCSE-help)
    http://www.edexcel.com/migrationdocu...e_20120525.pdf

    Ok guys a little help with 15 c) please?

    ' The smallest detail that can be seen on the image is half the length of the ultrasound
    pulse. The thumbnail on the fetus is 0.50 mm thick. The speed of ultrasound in the
    thumbnail is 2000 m s–1
    .
    Calculate the maximum pulse duration if the thumbnail is to be seen on the image'

    What does it mean by pulse length, and how is that different to pulse duration? And how do we go about solving this problem?

    Thanks a lot
    One pulse length=1 wavelength

    Speed=distance/time

    The pulse goes to the end in the thumbnail AND back.

    2000=0.001/ time

    Time=0.001/2000

    Time=5 X10^-7
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    (Original post by Randy123)
    does anyone on here know how to measure the rotation of the plan of polarisation and could explain to me please
    Yes I need this too...

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    (Original post by StUdEnTIGCSE)
    Yes I need this too...

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    Pass polarised light from an LED through sugar. The sugar rotates the plane of polarisation. Place a polarising filter at the end of the sugar then rotate it until maximum intensity is detected by eye. Measure this rotation using a protractor to get the correct angle difference. More sugar concentration means more rotation of polarising filter, so measured angle difference from protractor is bigger.
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    (Original post by Randy123)
    does anyone on here know how to measure the rotation of the plan of polarisation and could explain to me please
    Have a look on the June 11 paper. A question was asked there.
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    (Original post by krisshP)
    Pass polarised light from an LED through sugar. The sugar rotates the plane of polarisation. Place a polarising filter at the end of the sugar then rotate it until maximum intensity is detected by eye. Measure this rotation using a protractor to get the correct angle difference. More sugar concentration means more rotation of polarising filter, so measured angle difference from protractor is bigger.
    How do we know what is original angle of plane of polarisation?

    What is meant by the plane of polarisation? Is it the plane where the vibrations of the transverse wave is being confined to?
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    Is current ever inversely propertional to the voltage?
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    (Original post by StUdEnTIGCSE)
    How do we know what is original angle of plane of polarisation?

    What is meant by the plane of polarisation? Is it the plane where the vibrations of the transverse wave is being confined to?
    Say if plane of polarisation is horizontal, it means as unpolarised light passes through it, wave oscillations are restricted to the horizontal direction perpendicular to direction of wave travel.

    Say if plane of polarisation is vertical, it means as unpolarised light passes through it, wave oscillations are restricted to the vertical direction perpendicular to direction of wave travel.

    http://t1.gstatic.com/images?q=tbn:A...MzolMudU4VvrKw
    In there the first Polaroid has its plane of polarisation vertical.

    http://www.arborsci.com/CoolStuff/Reyleigh_Diagram.jpg
    Look at that
    You choose the first Polaroid orientation, so you determine the original angle of polarisation which is likely to be 0* vertical as shown there.
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    (Original post by Zoeyyy)
    Is current ever inversely propertional to the voltage?
    P=IV
    I=P/V

    So yes
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    (Original post by krisshP)
    P=IV
    I=P/V

    So yes
    Only if the power is constant

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    (Original post by krisshP)
    Say if plane of polarisation is horizontal, it means as unpolarised light passes through it, wave oscillations are restricted to the horizontal direction perpendicular to direction of wave travel.

    Say if plane of polarisation is vertical, it means as unpolarised light passes through it, wave oscillations are restricted to the vertical direction perpendicular to direction of wave travel.

    http://t1.gstatic.com/images?q=tbn:A...MzolMudU4VvrKw
    In there the first Polaroid has its plane of polarisation vertical.

    http://www.arborsci.com/CoolStuff/Reyleigh_Diagram.jpg
    Look at that
    You choose the first Polaroid orientation, so you determine the original angle of polarisation which is likely to be 0* vertical as shown there.
    Ah yes, get it now.
    So the original angle of polarisation is determined beforehand, using a fixed polaroid orientation.
    And the plane of polarisation is the plane in which the oscillations are being confined to perpendicular to the direction of travel of the wave.

    Thanks

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    (Original post by StUdEnTIGCSE)
    Ah yes, get it now.
    So the original angle of polarisation is determined beforehand, using a fixed polaroid orientation.
    And the plane of polarisation is the plane in which the oscillations are being confined to perpendicular to the direction of travel of the wave.

    Thanks

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    Yep
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    can someone tell me how to do this question please?
    Name:  mateo-6.jpg
Views: 255
Size:  280.4 KB answer is c but how?
    ignore the attatchment just the picture is necessary
    Attached Images
  1. File Type: pdf mateo.pdf (820.0 KB, 69 views)
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    (Original post by mnasmith)
    can someone tell me how to do this question please?
    Name:  mateo-6.jpg
Views: 255
Size:  280.4 KB answer is c but how?
    ignore the attatchment just the picture is necessary
    Go some pages back, the answer was posted with its explanation
 
 
 
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