1. The problem statement, all variables and given/known data A beam of spin 1/2 particles with speed v passes through a series of SGz devices. The first SGz device transmits particles with Sz = ħ/2 and filters out particles with Sz=-ħ/2. The second SGz device transmits particles with Sz=-ħ/2 and filters out particles of Sz=ħ/2. Between the two devices is a region of length l in which there is a uniform magnetic field B pointing in the x-direction. Determine the smallest value of l such that exactly 25% of the particles transmitted by the first SGz Device are transmitted by the second device. Express your result in terms of ω=egB/2mc and v. 2. Relevant equations 3. The attempt at a solution Because of the way particles are being passed through the two SGz devices doesn't only 25% of the particles pass through the second device regardless of the distance between the SGz devices? I know that's not exactly right but I'm failing understand why it's not right. I've been pulling my hair out. I have no idea where this 'l' variable is coming from. Any advice or direction would be appreciated.