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 tube User manual for electron diffraction tube (3B Scientific)
  • Physics Physics, John Willey & Sons, Inc. , David Halliday, Robert Resnick and Kenneth S. Krane 993 , (1992).
  • Modern Physics Modern Physics, Thomson learning , Raymond A. Serway, Clement J. Moses, and Curt A. Moyer 152 , (2005).

Pictorial Procedure

1. Provided apparatus (assembled view)

1. Provided apparatus (assembled view)

2. Tube holder with retaining sliders

2. Tube holder with retaining sliders

3. Inserting electron diffraction tube into the fork-shaped tube holder

3. Inserting electron diffraction tube into the fork-shaped tube holder

4. Electron diffraction mounted on a tube holder

4. Electron diffraction mounted on a tube holder

5. Connecting an ammeter in series with anode

5. Connecting an ammeter in series with anode

6. Making ground terminal common with cathode

6. Making ground terminal common with cathode

7. Making electrical connections for heater (6.3V AC)

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

8. Connecting cathode of the power supply to the 2mm connector of the electron diffraction tube

9. Rings formed on the fluorescent screen

9. Rings formed on the fluorescent screen

10. Converting an RGB image to gray scale

10. Converting an RGB image to gray scale

11. Finding the length of the reference line

11. Finding the length of the reference line

12. Finding the radius of the thing using the plugin ThreePointRO

12. Finding the radius of the thing using the plugin ThreePointRO