Introduction
In this science experiment, we will find out the effect of distance on radioactive source intensity and the effect of mass absorption of gamma and beta radiation.
We know that the intensity of a radioactive source decreases as the distance from the source increases. This is because radioactive particles or radiation emitted from the source are scattered or absorbed as they travel through space, causing the number of particles or amount of radiation to decrease with distance.
The rate at which the intensity of a radioactive source decreases with distance depends on several factors, including the type of radiation emitted by the source (e.g., alpha, beta, gamma), the energy of the radiation, the physical properties of the surrounding material, and the geometry of the source and surrounding environment.
It’s important to note that the effect of distance on radioactive source intensity is a fundamental principle in radiation safety and is used to determine safe distances for workers and the public in areas where radioactive sources are used or stored.
Basic Building Concept
1. When an atom breaks down or decays, it starts giving out energy, and this phenomenon is called radioactivity.
2. The elements that decay to give out energy are radioactive elements.
3. The radioactive source is the quantity of a radionuclide that gives out ionizing radiation such as gamma rays, alpha particles, beta particles, gamma rays, and neutron radiation.
4. Radioactive source intensity decreases with time by emitting more energy and acquiring a stable state. Its unit is Becquerel(Bq) and Curie(Cu).
5. The rays emitted from an element that consists of two protons and two neutrons are termed Alpha rays or alpha radiation. They are generally produced from the decay of alpha decay.
6. The radiation which arises from the radioactive decay of atomic nuclei is termed gamma rats or gamma radiation.
Aim
To determine the effect of distance on radioactive source intensity and the effect of mass absorption of gamma and beta radiation.
Theory
The relationship between distance and intensity is described by the inverse square law, which states that the intensity of radiation is proportional to the inverse square of the distance from the source. This means that if you double the distance from a radioactive source, the intensity of the radiation will decrease by a factor of four (i.e., 2^2). If you triple the distance, the intensity will decrease by a factor of nine (i.e., 3^2), and so on.
Inverse-square law states that a specified physical quantity, like intensity, is inversely proportional to the square of the distance measured from the source.
I ∝ (1/r²)
Requirements
1. Spectrum Techniques ST360 Counter
2. GM Tube
3. Power Supply
4. Stand
5. Clamp
6. USB Cable
7. Source Holder
8. 20 Shields of varying mass thickness
9. Sony Notebook Computer
10. 2 Radioactive Sources are Beta Sr-90 and Gamma Co-60.
Procedure
Step 1: On the clamp of the ruler stand, place a detector.
Step 2: On the surface of the table, place the radioactive source.
Step 3: Now, record at least ten reading at the interval of sixty seconds for each of the two sources from 2cm to 24cm at the interval of 1cm.
Step 4: For the Beta and Gamma experiment, inside the shelf stand, 3cm away from the detector, you have to place the source in the source holder,
Step 5: Now, 2cm away from the detector, place a shield.
Step 6: For each source and shield, record at least 10 readings at the interval of 60 seconds.
Observation
1. From the inverse square law and the Beta and Gamma experiment, we have observed that the intensity is inversely proportional to the distance square, and the plotted graph is obtained as a hyperbola.
2. Graph described intensity as proportional to the reciprocal of the square of the distance, and the obtained graph is a straight line.
3. Graph describes that the intensity decreases with the increase in the absorber mass thickness.
4. The graph of Beta radiation is straight, but the intensity decreases because of the aluminum shield.
5. Mass thickness of the number of the shield increases until the use of the thickest lead absorber.
6. Beta radiation is less penetrating than Gamma radiation.
7. Lead is a better absorber than aluminum based on the mass thickness.
8. For gamma rays, Half-thickness calculated was 6553 mg/cm^2.
Result
1. Intensity of radiation decreases with the increase in the distance through inverse square law.
2. Linear thickness and the material of increasing density increase radioactive shielding effectiveness.
Precautions
1. Plot the graph carefully.
2. Do not use radioactive sources for external use.
3. Handle this experiment with utmost care.
Conclusion
The results suggest that the intensity of radiation decreases proportionally as the inverse square of the distance and the effectiveness of radioactive shielding improves with materials of increasing density and linear thickness.
VIVA Questions With Answers
Q.1 What was the aim of this experiment?
ANS. To determine the effect of distance on radioactive source intensity and the effect of mass absorption of gamma and beta radiation.
Q.2 What do you understand about radioactivity?
ANS. When an atom breaks down or decays, it starts giving out energy, and this phenomenon is called radioactivity.
Q.3 What do you know about radioactive elements?
ANS. The elements which decay to give out energy are called radioactive elements.
Q.4 What do you understand about the radioactive source?
ANS. The quantity of a radionuclide that gives out ionizing radiation, such as gamma rays, alpha particles, beta particles, gamma rays, and neutron radiation, is called the radioactive source.
Q.5 What radioactive sources have we used in this experiment?
ANS. Beta Sr-90 and Gamma Co-60.
Q.6 What do you understand by inverse square law?
ANS. Inverse-square law states that a specified physical quantity that can be intense is inversely proportional to the square of the distance measured from the source.
I ∝ (1/r²)
Q.7 Is it true that lead is a better absorber than aluminum?
ANS. Yes, based on the mass thickness, lead is a better absorber than aluminum.
Q.8 What do you understand about gamma rays?
ANS. The radiation which arises from the radioactive decay of atomic nuclei is termed gamma rays or gamma radiation.
Q.9 What do you understand about alpha rays?
ANS. The rays emitting from an element that consists of two protons and two neutrons are termed Alpha rays or alpha radiation. They are generally produced from the decay of alpha decay.
Q.10 Name the unit radioactive source intensity.
ANS. Becquerel(Bq) and Curie(Cu).
Saquib Siddiqui is a Mechanical Engineer and a content creator. He has special interest in science experiments and teaches the same to school and college students. He is also a technical lead at RUDE LABS PVT. LTD.
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