Question

A device used for the measurement of radioactivity is:
A) Mass spectrometer
B) Cyclotron
C) Barometer
D) G.M. Counter

Answer 1

Hint: the radioactivity is a process of emission of radioactive particles. The radioactivity can be measured in terms of the electric current. The device converts the ionization power of radioactive particles into the current. The radioactivity measurements are used to determine the amount of radiation emitted or absorbed by the person. This has wide application in the nuclear industry, hospitals, etc.

Complete step by step answer:
A nuclear process in which an unstable nucleus emits the radioactive particles and energy is known as the radioactive process. The substances which release energy are called the radioactive substance.
The radioactivity is measured by the Geiger –Muller counter (G.M.Counter). The GM counter is used to detect the radioactive emission, most commonly for gamma and beta particles.
-Principle: When the ionized particles pass through the Geiger Muller tube, the particle ionizes the gas, and the electrons produced due to ionization are attracted to the positively charged electrode. These high-speed electrons later produce the secondary electrons with the collision of gas particles. This process of electrons production is in geometric progression. The current developed at the GM counter is directly related to the radioactivity of an ionizing particle.
-Construction: The G.M. counter is as shown below,

Working:
When radioactive particles like beta or gamma particles are allowed to pass through the ionization chamber, the highly energetic radioactive particles collide with the atoms of inert gas. This collision results in the production of a primary electron. These primary electrons are highly energetic and move towards the positively charged electrode, the anode. These primary electrons further collide with the gas atoms to generate the secondary electrons. The electrons are attracted to the high-voltage middle wire (Anode). The large number of electrons are built around the wire and as soon as it reaches the threshold, the electric current starts to flow through the external circuit. This electric pulse is recorded by the load. This signal is intensified as the ionization radiation increases. The G.M.Counter is used to determine the amount of radioactive material that is emitted or absorbed by. The unit for radioactive emission is Becquerel .The Becquerel is equal to the number of decay per second.
The G.M.Counter is used to measure radioactivity.

Hence, (D) is the correct option.

Note: Apart from the Geiger Muller counter there are other devices to measure the radioactivity of an ionization. These are as follows,
1) Ionisation chamber: This is an air filled chamber. The radiation ionizes the gas molecules and produces the corresponding current.
2) Photodetectors
3) Scintillation detector
4) Semiconductor detector
5) Dosimetry