1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Applications of Mass Spectrograph

  1. Jul 25, 2006 #1
    # A mass spectrograph determines:
    a)spectrum of light
    b)charge of the ion
    c)specific charge of positive rays
    d)specific charge of cathode rays
    I know that a mass spectrograph has been used to determine the specific charge of positive ions and we may get 1, 2, 3… Parabola’s depending on the number of isotopes the element under study has. But, can it be used to determine the specific charge of cathode rays?
  2. jcsd
  3. Jul 25, 2006 #2

    Andrew Mason

    User Avatar
    Science Advisor
    Homework Helper

    Cathode rays are electrons. A mass spectrometer measures charge to mass ratios of ions, so c) should be the correct answer. I don't know about the use of the word "rays" though.

  4. Jul 25, 2006 #3


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    C is wrong... cathode rays is choice D. I would say B... it doesn't give yuo the specific charge of a cathode ray, because you don't know how many electrons are flowing (it just gives you the relative charge to mass ratio). But the charge of an ion.... presumably, you know the mass by looking it up on a periodic table.

    To make it a bit clearer (that's rambling up above):

    If you use it for a ray, because you don't know how many particles are in the ray, you're only capable of measuring the ratio of charge to mass. However, if you measure the ratio of charge to mass for an ion, you can calculate the charge by figuring out the mass given the composition
  5. Jul 27, 2006 #4
    Thanks for the help.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook