# Mass Spectrometer

1. Jun 5, 2005

### scorpa

Hey Everyone,

I just got to my last homework question, and well I got a bit stuck.

An ion source contains two isotopes of magnesium ( 24Mg, 25Mg). These ions travels undeflected through the velocity selector (B=0.850T, [E]=4.60x10^5V/m) of a mass spectrometer. If both isotopes are singly charged, how far apart are the lines on the ion deflector? Assume magnetic field strength in the ion separator in 0.250T.

First I went v=E/B 4.60x10^5V/m / 0.850T = 5.41x10^5m/s

Then I went Bv=E to find the new electric field

(0.250T)(5.41x10^5m/s) = 1.35 x 10^5 V/m

Now I really don't know what to do, or if that was even right. I know to find the distance I need to use the equation d=V/[E] but I just can't seem to get the right answer. Apparently the answer should be 0.045m. Thanks for any help you can give.

2. Jun 5, 2005

### scorpa

Ok I went through it again and decided that to find my Voltage I needed to use change in energy over charge =V, so I went through and found the energy and divided by elementarty charge, then I put it into the equation d=V/electric field and still couldn't get hte answer, I am so lost!