Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Proton Beam therapy (magnetic field)

  1. Oct 28, 2008 #1
    1. The problem statement, all variables and given/known data
    A beam of protons with v=1.8x10^8 are deflected 90 degrees by a constant magnetic field. The trajectory of the beam has a circular arc with a radius of 4m.

    I am asked to find the magnitude of the constant magnetic field.

    2. Relevant equations

    I know that r=mv/eB. When solving for B the equation is B=mv/er. Right?

    3. The attempt at a solution

    This gives me 7.515 for the magnitude of the magnetic field. The correct answer is 0.47T.
    Did I start with the wrong equation?
  2. jcsd
  3. Oct 28, 2008 #2


    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper

    Welcome to PF.

    You may have entered a number wrong. Using your values I get 0.47T as well.
  4. Oct 28, 2008 #3
    Ahh... I see.

    That was easy. Thanks!
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook