Introduction to Geiger Counter:

The Geiger-Mueller tube is the main part of the Geiger counter apparatus which is used in this experiment. The radioactive source for the experiment is Cesium-137.

Hans Geiger, along with Rutherford identify the nucleus after whom the tube is referred to as a GM tube. The tube is in the shape of a cylinder about 1 cm in diameter and about 4 cm long. We carry the Cesium-137 source close to the end of the Geiger-Mueller tube.

The main features of the source:

  • The half-life for the cesium-137 decay is 30.2 years
  • The source activity was 5 micro Curies when new (1 Curie = 3.7 x1010decays per second)
  • The energy of the emitted gamma rays is 661.6 K eV (1 KeV = 1 thousand electron-volts).

Geiger counter Viva Questions

Some Viva questions are listed here related to the Geiger counter:

  1. What interval did you select to note the counts?
  2. What is the minimum number of counts detected in that interval?
  3. Cesium-137 decays into Barium or Uranium?
  4. When Cesium-137 decays, which particles eject?
  5. From which excited nuclei photon emits, the Cesium-137 or Barium-137?
  6. Why should you clean the hand after performing the experiment?
  7. What precaution you should keep when performing the Geiger-Mueller experiment?

Questions working of Geiger-Muller Tube

  1. In which region the GM TUBE cannot distinguish between different type of radiations and why?
  2. A metal wire that is stretched at the axis of the cylinder (GM TUBE) is Anode or Cathode?
  3. This tube is filled by what type of gas and some volatile compounds?
  4.  The potential difference between the anode and cathode of the tube is of what order?
  5. What type of particles this detector can detect?
  6. Can we detect the counts of radiation without the ionization inside the tube?
  7. Does the cylindrical geometry of the tube play any role to define the electric field in the tube? If yes, where it will be maximum?

Part -2 of working

  1. The Townsend avalanche created due to the high electric field, where it takes place?
  2. For the second avalanche which particle is responsible within the G M TUBE?
  3. What is Geiger’s discharge?
  4. What do you understand from photo-electron in the tube and how they emit?
  5. Does photo-electron initiate the second avalanche?
  6. In the G M TUBE does every avalanche initiate the next avalanche, if yes what is the main point behind it?
  7. From mass points of view, at a constant potential difference does two different massive particles will move at the same speed?
  8. A space charge produces near to the central wire during the avalanche process, is this space charge created by the electrons or by the positive ions?
  9. The Geiger discharge repeated at fix interval of time, what is the reason for it?
  10. What is the concept of voltage drop, and how it helps to detect the rate of ionizing radiation?
  11. What do you mean by the characteristic curve for the counter? What it reflects?


If you want to know more about the Geiger-Muller tube and its working, let me know. You can write your question in the comment box below.

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