# Thomson's Apparatus

1. Oct 16, 2012

### ElijahRockers

1. The problem statement, all variables and given/known data

The question at the top of this PDF is kinda confusing me... I follow it all the way up until it says

$sin\theta \approx \theta \equiv \frac{l}{r} \Rightarrow r \approx \frac{l}{\theta}$

3. The attempt at a solution

The book I'm using has an identical question (same values even) as this one, but it refers me to "Figure 4.6" which is supposed to be a diagram of the Thomson apparatus in question, but it's not in the book as far as I can tell. I did find a diagram of the apparatus at the beginning of the chapter with a somewhat similar example, (except the book uses tan(theta), and no magnetic field, only uses the electric field) but I'm wondering why we are using sine in the PDF.