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Edexcel Physics Unit 3 9th May Watch

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    (Original post by StUdEnTIGCSE)
    Prefix are considered part of a unit so microm^-1 is 1/microm, which makes sense.

    Its a wave number, we studied this in Chem. I might have got confused

    Posted from TSR Mobile
    1/micro is mega.

    I didn't study it anywhere, but it makes mathematical sense really :dontknow:

    I'll demonstrate this with an example.

    The first wavelength was 630 nanometres I believe, and the inverse given was 1.59.

    Let's make this simple and convert it all to SI units first.

    630 nanometres is 630 \times 10^{-9} \mathrm{ \ m} = 6.3 \times 10^{-7} \mathrm{ \ m}.

    Inverse this, and we get 1590000 m-1 to 3 s.f.

    Which is 1.59 Mega m-1!
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    (Original post by justinawe)
    1/micro is mega.

    I didn't study it anywhere, but it makes mathematical sense really :dontknow:

    I'll demonstrate this with an example.

    The first wavelength was 630 nanometres I believe, and the inverse given was 1.59.

    Let's make this simple and convert it all to SI units first.

    630 nanometres is 630 \times 10^{-9} \mathrm{ \ m} = 6.3 \times 10^{-7} \mathrm{ \ m}.

    Inverse this, and we get 1590000 m-1 to 3 s.f.

    Which is 1.59 Mega m-1!
    Wrong!
    How did you state it in the answer?
    Mm^-1?
    That's wrong ( but they might accept!)
    Real way is to put as micro+meter+^-1 (no spaces in between)
    Don't get me wrong!
    I know that the correct answer is 10^6 * m^-1 but you can't simply replace 10^6 with M.
    What you can do is replace it with (micro symbol) .it will be treated as a part of the unit.
    HERE IS SOME PROOF:
    6.2.3 Inseparability of prefix and unit The grouping formed by a prefix symbol attached to a unit symbol constitutes a new inseparable symbol (forming a multiple or submultiple of the unit concerned) which can be raised to a positive or negative power and which can be combined with other unit symbols to form compound unit symbols. Examples: 2.3 cm3 = 2.3 (cm)3 = 2.3 (10−2 m)3 = 2.3 × 10−6 m3 1 cm−1 = 1 (cm)−1 = 1 (10−2 m)−1 = 102 m−1 5000 µs−1 = 5000 (µs)−1 = 5000 (10−6 s)−1 = 5000 × 106 s−1 = 5 × 109 s−1 1 V/cm = (1 V)/(10−2 m) = 102 V/m Prefix names are also inseparable from the unit names to which they are attached. Thus, for example, millimeter, micropascal, and meganewton are single words
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    (Original post by TheKingOfTSR)
    Wrong!
    How did you state it in the answer?
    Mm^-1?
    That's wrong ( but they might accept!)
    Real way is to put as micro+meter+^-1 (no spaces in between)
    Don't get me wrong!
    I know that the correct answer is 10^6 * m^-1 but you can't simply replace 10^6 with M.
    What you can do is replace it with (micro symbol) .it will be treated as a part of the unit.
    HERE IS SOME PROOF:
    6.2.3 Inseparability of prefix and unit The grouping formed by a prefix symbol attached to a unit symbol constitutes a new inseparable symbol (forming a multiple or submultiple of the unit concerned) which can be raised to a positive or negative power and which can be combined with other unit symbols to form compound unit symbols. Examples: 2.3 cm3 = 2.3 (cm)3 = 2.3 (10−2 m)3 = 2.3 × 10−6 m3 1 cm−1 = 1 (cm)−1 = 1 (10−2 m)−1 = 102 m−1 5000 µs−1 = 5000 (µs)−1 = 5000 (10−6 s)−1 = 5000 × 106 s−1 = 5 × 109 s−1 1 V/cm = (1 V)/(10−2 m) = 102 V/m Prefix names are also inseparable from the unit names to which they are attached. Thus, for example, millimeter, micropascal, and meganewton are single words
    I wrote 10^6 \mathrm{ \ m }^{-1}
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    (Original post by StUdEnTIGCSE)
    Prefix are considered part of a unit so microm^-1 is 1/microm, which makes sense.

    Its a wave number, we studied this in Chem. I might have got confused

    Posted from TSR Mobile
    I think your correct!
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    (Original post by StUdEnTIGCSE)
    Prefix are considered part of a unit so microm^-1 is 1/microm, which makes sense.

    Its a wave number, we studied this in Chem. I might have got confused

    Posted from TSR Mobile
    Actually, after thinking about it, I believe you are right. My friends who wrote Mega m-1 managed to convince me they were right, but now I'm pretty sure they were wrong
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    (Original post by Aerosports)
    Unofficial mark scheme:
    1)B 2) D 3)C 4)B 5) C

    6) Disscus Advantages and DIs advantages about uncertainty

    7)Experiment for Spring constant

    8) m = hc/e c = speed of light, e = electron charge

    8 part c) Graph ,part d) find plancks constant ,part e)Suggest difference between real constant and your given constant i calculated 5.54x10 -34



    btw the way i finished 20mins early
    How did you get 5.54x10^-34?
    What did you get for gradient. I got one hence I got h to be 5.3x10^-28
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    (Original post by thextractor007)
    How did you get 5.54x10^-34?
    What did you get for gradient. I got one hence I got h to be 5.3x10^-28
    You forgot to consider the fact that the inverse wavelength wasn't in SI unit.
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    My graph went through origin, cutting 3 points but I used a scale of 1 every 10 squares, so my gradient was 0.68

    Got planks constant as 3.x * 10^28. Didn't multiply it by 10^6 either...

    How much do you reckon I'll get for graph + plank constant out of 11?

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    i got h = 4.1x10^-34
    almost everyone in class got that as well...
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    (Original post by Relaxedexams)
    My graph went through origin, cutting 3 points but I used a scale of 1 every 10 squares, so my gradient was 0.68

    Got planks constant as 3.x * 10^28. Didn't multiply it by 10^6 either...

    How much do you reckon I'll get for graph + plank constant out of 11?

    Posted from TSR Mobile
    1028 or 10-28? If it's the former, then that's way off.

    Hmm, why would the scale change your gradient? It shouldn't make a difference what scale you'd use.

    If you plotted the points correctly and did everything else right, it's probably an issue with your best fit line. I'd say 8 or 9 out of 11, if you did everything else right.
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    (Original post by Meera.S.)
    i got h = 4.1x10^-34
    almost everyone in class got that as well...
    Yeah, I got 4.00 x 10-34... I'm not too sure how some people on here got more than 5
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    (Original post by Relaxedexams)
    My graph went through origin, cutting 3 points but I used a scale of 1 every 10 squares, so my gradient was 0.68

    Got planks constant as 3.x * 10^28. Didn't multiply it by 10^6 either...

    How much do you reckon I'll get for graph + plank constant out of 11?

    Posted from TSR Mobile
    Maybe 9?
    - goes through origin(1)
    - the axis (1)
    -the triangle for the gradient(1)
    - you did the y=mx+c (3)
    - you found the inverse of the wavelengths (3)
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    (Original post by justinawe)
    1028 or 10-28? If it's the former, then that's way off.

    Hmm, why would the scale change your gradient? It shouldn't make a difference what scale you'd use.

    If you plotted the points correctly and did everything else right, it's probably an issue with your best fit line. I'd say 8 or 9 out of 11, if you did everything else right.
    10^-28

    I suppose its the line of best fit then.

    So 1 mark each for line of best fit, wrong gradient, not changing units to SI by multiplying by 10^6, and wrong final planck constant? I also put unit as Js without converting to SI. Will I get docked a mark for that too?
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    i got 100 Hz for the mcq
    how is the answer 250 Hz? ;/
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    (Original post by justinawe)
    Yeah, I got 4.00 x 10-34... I'm not too sure how some people on here got more than 5
    I got 3.63! Which is much closer to your value than the others at my school. Most of them got 5!

    I suppose its because they didn't cut through the origin, so their gradient was larger, leading to a higher planck constant.

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    (Original post by Relaxedexams)
    I got 3.63! Which is much closer to your value than the others at my school. Most of them got 5!

    I suppose its because they didn't cut through the origin, so their gradient was larger, leading to a higher planck constant.

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    if i were you, i would have rounded and gotten 4
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    i got some what 5.4*10^-34 it should be correct ans because it close to the original value also i tripled checked cause i finished the exam 15 earlier.
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    (Original post by justinawe)

    Hmm, why would the scale change your gradient? It shouldn't make a difference what scale you'd use.
    Well for those 1.4, 6.3 values, I rounded off and plotted points due to my scale which was congested, so gradient w ould have changed right?

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    (Original post by Meera.S.)
    i got 100 Hz for the mcq
    how is the answer 250 Hz? ;/
    well each sqaure was 1ms, and a complete wave lenght was for 4ms that's the period for one wave lenght is 4*10-3 sec so to get frequency just inverse it
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    (Original post by ramanan)
    i got some what 5.4*10^-34 it should be correct ans because it close to the original value also i tripled checked cause i finished the exam 15 earlier.
    There will be a range of acceptable answers. Your value depends on how you drew your line of best fit, so naturally not everyone would arrive at the same answer.
 
 
 
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