Magic eye

From Physlab.lums.edu.pk

Imaging electron trajectories: e/m measurement with a magic eye and ImageJ (1.15)

Students Manual	A magic eye is a simplistic triode tube that was used as a tuning indicator in radio receivers around the time of the World-War II. It has a bowl shaped anode coated with a phosphorescent material that produces a green glow when electrons strike on it. In this experiment, we measure the radius of curvature of the path of electrons in a magnetic field using a freeware, open-source image processor ImageJ, and calculate the charge-to-mass ratio of the electron.
ImageJ Software	ImageJ
Threepoint Plugin	ThreePointCircularROI
Sample Results	Image processing in ImageJ A graph for finding the e/m ratio
Further Readings and References	Quantum Physics D. Prutchi, and S. Prutchi, Exploring Quantum Physics through Hands-on Projects, John Wiley, Inc., pp. 77-79 (2003). ImageJ_link W.S. Rasband, ImageJ, U. S. National Institutes of Health, Bethesda, Maryland, USA, 1997-2012. Error Analysis John R. Taylor, An Introduction to Error Analysis, University Science Books, 1997, Ch. 8.

1. Make sure you have the needed apparatus	2. Make connections to the tube. The numbering on the white base will help. Consult manual for description of pins.
3. Set the magic eye filament and the field coil voltage.	4. Set a value on the high voltage DC supply.
5. Measure the magnetic field inside the coil using a Gauss-meter and its axial probe.	6. Take photographs for analysis, for several voltages from the High voltage supply.