GM Counter Experiment Questions and Answers for Viva

Answer-1: A Geiger counter is a tool which is used to detect and measure particles in ionised gases. It detects the nuclear radiations (alpha, beta particles, etc...) by the ionization produced in low pressure gas in a G.M.tube. It is extensively employed in applications like radiological protection, radiation dosimetry, and experimental physics.

Answer-2: Hans Geiger and Walther Müller invented the Geiger counter.

Answer-3: The Geiger counter is dictated entirely by the design of the tube and can be generally categorised into two types, End Window and Windowless.

Answer-4: It works on the principle of “Gas multiplication”. The Geiger-Müller tube is filled with a gas such as neon, argon, or helium at the pressure being the lowest, where there is an application of high voltage. There would be the conduction of the electrical charge on the tube when a particle or photon of incident radiation would turn the gas conductive by means of ionisation.

Answer-5: Ans: Ionization in a gas is caused by the entry of photon. The ions are attracted to their appropriate electrodes and they gain sufficient energy to eject electrons from the gas atoms as they pass through the gas. This causes the atoms to ionize, therefore electrons are produced continuously by this process and rapid gas multiplication takes place. Therefore electrons create pulses which than can be amplified and counted using G.M. counter.

Answer-6: It is the process of removal of electrons from the atom. It is the conversion of a substance, molecule or atom into an ion or ions, using by eliminating one or more electrons.

Answer-7: The process of removal of all the ions from the chamber by the continuous discharge and make it ready for the fresh event. G.M.counter is a gas ionization detector.

Answer-8: These are the counts due to the secondary cosmic rays present in the atmosphere.

Answer-9: When the primary cosmic rays enter the earth’s atmosphere, they ionize the medium producing the charged particles, these are the secondary cosmic rays.

Answer-10: This is the section of the G.M characteristics curve constructed with counting rate v/s applied voltage over which the counting rate is substantially independent of the applied voltage. Unless otherwise stated the plateau is measured at a counting rate of an approximately 100 counts.

Answer-11: This is the lowest applied voltage which corresponds to the start of the plateau for the stated sensitivity of the measuring circuit.

Answer-12: This is the range of applied voltage over which the plateau region extends. Upper threshold voltage (V2 ): This is the higher voltage up to which plateau extends buy on which count rate increase with increase in applied voltage.

Answer-13: This is the change in counting rate over the plateau length, expressed in % per volume.

Answer-14: It is the thickness of the absorbing material at which the intensity of radiation entering it is reduced by half of its original value.

Answer-15: It consists of ?-particles which are high-energy, high-speed electrons or positrons emitted by certain type of radioactive nuclei. Beta rays are formed by beta decay. Beta rays consists of negatively charged particles. Gamma particles are electrically neutral. The source of beta ray used is Thallium. G.M. counters are also used in nuclear industries, geological exploration, radiation dosimeter, etc.

Answer-16: It is unable to measure high radiation due to dead time of tube.

Answer-17: This is an insensitive period after each ionization of gas during which any incident radiation will not result in a count.

Answer-18: This is the lowest applied to a G.M tube at which pulses just appears across the anode resistor unit starts counting.

Answer-19: This is the supply voltage at which G.M tube should preferable be used. This voltage in normally chosen to be in the middle of plateau.

Answer-20: Photon emitted by excited atomic nucleus decaying to a lower energy state gamma radiation as a line spectrum with photon energy which are specific to the nuclide concerned. Gamma and X-rays are both electromagnetic radiation & they are distinguished only by this made of generation