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Quantum phsics and x-ray physics

  1. May 2, 2005 #1
    is there anyone on here who could help me out with either of these?
     
  2. jcsd
  3. May 2, 2005 #2
    heres a sample question
    Calculate the de Broglie wavelength of a 5,000 kg truck traveling at 80 kph. (Round answer to nearest hundredth.)
     
  4. May 2, 2005 #3

    StatusX

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    Help you with what? Are you doing a project? Or do you just have a bunch of questions? Just post your questions and people will help you with them. For the one above, that's just plug and chug. The formula for deBroglie wavelength is p = h/λ, where h is plancks constant.
     
  5. May 2, 2005 #4
    λ=5.97x e-39
    tahts the answer now how did i get it
    and i have alot of questions like this i just dont know how they are done
     
  6. May 2, 2005 #5
    ill post 2 mroe then i have to go for a while
    Calculate the uncertainty of the velocity of a particle confined to a space of 10-9 m if the particle is an electron
    (me = 9.1 · 10-31 kg)

    delta v=__________m/sec

    and


    Calculate the uncertainty of the velocity of a particle confined to a space of 10-9 m if the particle is a proton
    (mp = 1.7 · 10-27 kg)

    delta v=___________m/sec


    tahnks for your help
    btw if you didnt get this already i want how to get the answer not the answer
     
  7. May 2, 2005 #6

    StatusX

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    There are no concepts here. You just find p (which is m*v), look up the value for h, plug them in, and solve for λ. Feel free to ask any other questions right here, you don't need to ask for permission.
     
  8. May 2, 2005 #7

    StatusX

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    Are you asking where the formula comes from? If so, that's a little complicated, but I can give you a rough sketch.

    If you're asking how to plug numbers into a formula, you need to take a lot more math classes before you get into QM.
     
  9. May 2, 2005 #8
    m and v mass and velocity
    is that right? so the answer would be 5000*80*6.63e-34 correct? but it doesnt get the correct answer

    and yes i know how to as you say "plug and chug"
     
  10. May 2, 2005 #9

    StatusX

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    p=h/λ, so λ=h/p. Why are you doing these problems if you're still not comfortable with basic high school physics and math?
     
  11. May 3, 2005 #10
    that still doesnt get the correct answer
    λ=h/p
    6.63e-34/(5000*80) =λ doesnt get the correct answer so either your wrong or you jsut dont get what im asking for can you do teh question if so past your work on this page thats all i ask for
     
  12. May 3, 2005 #11

    O_o

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    Make sure everything is in SI units before you start solving.
     
    Last edited: May 3, 2005
  13. May 3, 2005 #12

    Gokul43201

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    No, whiteshado : StatusX is perfectly correct.

    You need to learn the following things first (way before you do Quantum Physics) :

    1. Basic algebra and arithmetic
    2. Units and dimensions

    take care of these and you'll be able to handle the first problem.

    We will not provide answers/solutions to your problems. That is not what this forum is meant for. If you need help with specific concepts, ask away, but if you have homework to do, we can not help unless you show what effort you have made.
     
  14. May 3, 2005 #13
    no i have the answers i posted the answer
    λ=5.97x e-39
    but how did i get it?
     
  15. May 3, 2005 #14
    ok how about a simpler one i need the equation for finding the frequency for a wavelength
     
  16. May 3, 2005 #15

    dextercioby

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    What's the SI unit for velocity ?

    Daniel.
     
  17. May 3, 2005 #16
    The answer you give is meaningless. You have no units (unless that x you have is not "times" but some constant with a unit). Wavelength is not dimensionless.
     
  18. May 3, 2005 #17
    Calculate the de Broglie wavelength of a 5,000 kg truck traveling at 80 kph
    λ=5.97 e-39m
     
  19. May 3, 2005 #18

    dextercioby

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    Alright.Now did u find out how to derive this result...?

    Daniel.
     
  20. May 3, 2005 #19
    sigh taht is waht i am trying to find out... but no one reads on this fourm

    and someone said im am just trying to get people to do my homework well how many people who want their homework done post the answer to their questions
     
  21. May 3, 2005 #20

    dextercioby

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    You've been told that

    [tex] \lambda \ \left(\mbox{m}\right)=\frac{h \ \left(\mbox{Kg}\cdot\frac{\mbox{m}}{\mbox{s}^{2}}\cdot\mbox{m}\cdot\mbox{s}\right)}{p \ \left(\mbox{Kg}\cdot\frac{\mbox{m}}{\mbox{s}}\right)} [/tex]

    Now plug the values paying attention to the units.Planck's constant is given in [itex] \mbox{J}\cdot\mbox{s} [/itex] which u can show to be equal to [itex] \mbox{Kg}\cdot\frac{\mbox{m}}{\mbox{s}^{2}}\cdot\mbox{m}\cdot\mbox{s}[/itex].

    U need to find the truck's momentum in SI units.Basically,u need to convert its speed from [itex] \frac{\mbox{Km}}{\mbox{hr}} [/itex] to [itex] \frac{\mbox{m}}{\mbox{s}} [/itex].

    Daniel.
     
    Last edited: May 3, 2005
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