| Student Manual |  This experiment utilizes a highly evacuated electron diffraction tube to study the wave-like properties of electrons. The electrons are emitted by the thermionic emission and accelerated towards target by applying a very high potential (2000-5000 V). The target is a micro meshed nickel grid on which a thin layer of graphite is deposited. The electrons being diffracted through the graphite satisfy the Bragg's condition and produce an interference pattern consisting of two rings. To measure the diameter of the ring, digital photographs are taken of the screen and analysis is done using a freely available software ImageJ. This experiment familiarize our students with digital photography and they will learn about its implications in experimental physics. |
| Software Code | 3point_ROI |
| Sample Results | A graph for the diameter of the rings versus accelerating voltage to find the inter-planar spacing |
| Experiment Code | 1.14 |
| Version | 29 September 2015, 2015-v2 |
Further Readings and References
- Electron diffraction tubeUser manual for electron diffraction tube (3B Scientific), .
- PhysicsPhysics, John Willey & Sons, Inc., David Halliday, Robert Resnick and Kenneth S. Krane, 993, (1992).
- Modern PhysicsModern Physics, Thomson learning, Raymond A. Serway, Clement J. Moses, and Curt A. Moyer, 152, (2005).
Pictorial Procedure
1. Provided apparatus (assembled view)
2. Tube holder with retaining sliders
3. Inserting electron diffraction tube into the fork-shaped tube holder
4. Electron diffraction mounted on a tube holder
5. Connecting an ammeter in series with anode
6. Making ground terminal common with cathode
7. Making electrical connections for heater (6.3V AC)
8. Connecting cathode of the power supply to the 2mm connector of the electron diffraction tube
9. Rings formed on the fluorescent screen
10. Converting an RGB image to gray scale
11. Finding the length of the reference line
12. Finding the radius of the thing using the plugin ThreePointRO