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    Hi guys can someone help me with the below:

    The muon has a mass equal to 207 times the mass of an electron. Calculate the speed of muons with the same de Broglie wavelength as the electrons in part b (i.e. 1.6 × 10–9 m).

    The answer is below but I was wondering if someone could explain why 1.6 × 10–9 m (the db wavelength from part b) becomes 1.6 × 10–7 ? and also why the answer is 2200. When I type in the same numbers into my calculator, I get 21.9737....


    (207 × 9.11 × 10-31) × v = (6.63 × 10-34)/(1.6 × 10-7)
    v = 2200 (2170)


    If someone could explain this to me, I'd be so grateful! Thank you!
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    (Original post by juicedesuccess)
    Hi guys can someone help me with the below:

    The muon has a mass equal to 207 times the mass of an electron. Calculate the speed of muons with the same de Broglie wavelength as the electrons in part b (i.e. 1.6 × 10–9 m).

    The answer is below but I was wondering if someone could explain why 1.6 × 10–9 m (the db wavelength from part b) becomes 1.6 × 10–7 ? and also why the answer is 2200. When I type in the same numbers into my calculator, I get 21.9737....


    (207 × 9.11 × 10-31) × v = (6.63 × 10-34)/(1.6 × 10-7)
    v = 2200 (2170)


    If someone could explain this to me, I'd be so grateful! Thank you!
    Do you understand the equations?

    



p = \dfrac{h}{\lambda}

    but  p = mv

    \Rightarrow mv = \dfrac{h}{\lambda}

    Do you have a screenshot of the question? When I use \lambda = 1.6 \times 10^{-9} I get the correct answer.
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    (Original post by juicedesuccess)
    Hi guys can someone help me with the below:

    The muon has a mass equal to 207 times the mass of an electron. Calculate the speed of muons with the same de Broglie wavelength as the electrons in part b (i.e. 1.6 × 10–9 m).

    The answer is below but I was wondering if someone could explain why 1.6 × 10–9 m (the db wavelength from part b) becomes 1.6 × 10–7 ? and also why the answer is 2200. When I type in the same numbers into my calculator, I get 21.9737....


    (207 × 9.11 × 10-31) × v = (6.63 × 10-34)/(1.6 × 10-7)
    v = 2200 (2170)


    If someone could explain this to me, I'd be so grateful! Thank you!
    v=h/mλ

    It does not become 1.6 × 10–7.

    Subbing in the de Broglie wavelength of the electrons you calculated before will give you the right answer.
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    Hi - thanks so much for your reply. Yes I understand the equations and the rearrangement of the equation - I just get stuck on why the de broglie wavelength has been multiplied by 100 in the question! Also I don't know how the answer of 2200 has been arrived at !! Mine is 21.9... even if I put in the figures as suggested in the answer!

    I've attached a screen shot if that helps... Thank you!
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    (Original post by juicedesuccess)
    Hi - thanks so much for your reply. Yes I understand the equations and the rearrangement of the equation - I just get stuck on why the de broglie wavelength has been multiplied by 100 in the question! Also I don't know how the answer of 2200 has been arrived at !! Mine is 21.9... even if I put in the figures as suggested in the answer!

    I've attached a screen shot if that helps... Thank you!
    I think it is a typo in the mark scheme if they are using 1.6 x 10^(-7), if you use 1.6 x 10^(-9) you get the correct answer! I tried myself.
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    (Original post by particlestudent)
    v=h/mλ

    It does not become 1.6 × 10–7.

    Subbing in the de Broglie wavelength of the electrons you calculated before will give you the right answer.

    Thank you!
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    (Original post by lizard54142)
    I think it is a typo in the mark scheme if they are using 1.6 x 10^(-7), if you use 1.6 x 10^(-9) you get the correct answer! I tried myself.
    Ah ok!!! Thank you! Stupid mark scheme! thanks again
 
 
 
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