Physics 101

Radioactivity

Background Radiation

Traces of radiation are present all around us.
It is not harmful, and it cannot pass through our skin.
Its activity varies from 20 to 40 counts/second.
Sources of this radiation are outer space (cosmic radiation), nuclear tests and reactors, radioactive rocks, some medicines, and some food.

Types of Radiation

Alpha ( $\alpha$ ): Helium Nucleus, positively charged: $\mathbf{_{2}^{4}\textrm{He}}$
Beta ( $\beta$ ): Electrons, negatively charged: $\mathbf{_{-1}^{0}\textrm{} \beta}$
Gamma ( $\gamma$ ): High frequency electromagnetic radiation
The particles are emitted in nuclear reactions (fission, fusion, and artificial transmutation) and in radioactive decay.
The spontaneous emission of alpha ( $\alpha$ ), beta ( $\beta$ ), and gamma ( $\gamma$ ) particles, independent of temperature and pressure, by radioactive nuclei is called radioactive decay.
This emission leads to increasing the stability of radioactive nuclei.
Emissions are random, so the order of emissions of these particles can only be predicted with probabilities.

5.2.2 Radioactive Emissions

$\boldsymbol{\alpha-, \beta -, \gamma - }$ emission Uses

$\boldsymbol{\alpha- }$ Particles:

Smoke detection
- Radioactive materials release -particles which ionizes the air inside the detector.
- Smoke from a fire absorbs -radiation altering the Ionization and triggering the alarm.

$\boldsymbol{\beta - }$ Particles:

Doctors use radioactive chemicals tracers for medical imaging.
- An isotope that emits particles can be injected in the bloodstream and its motion can be monitored by using a detector outside the body.
- Accumulation of the particles at any point in the blood stream will indicate a blockage.
particles are used in detectors that monitor and control the thickness of materials such as paper, plastic, and aluminum.
- The thicker the material, the more radiation is absorbed, and less radiation reaches the detector.
- It then sends signals to the equipment that adjust the thickness of the material.

$\boldsymbol{ \gamma - }$ Radiation:

5.2.3 Radioactive Decay and Half Life

Heavy radioactive isotopes decay into lighter isotopes of higher stability until they decay into lead, which is the most stable element.
The time it takes for half of a sample of radioactive isotopes of an element to decay is known as the Half Life ( ).
This yields an exponential graph of radioactive decay.

5.2.5 Safety Precautions

Wearing protective clothing.
Keep as far away as practical, e.g. use tongs.
Keeping your exposure time as short as possible.
Keeping radioactive materials in lead-lined containers, labelled with the appropriate hazard symbols.

Waste

Low-Level radioactive waste, such as contaminated gloves, can be disposed of in landfill sites.
But higher-level waste, which may be dangerously radioactive, is difficult to dispose of.
It can be reprocessed to extract nuclear fuel or encased in lead and left deep underground.

Precautions with usage of Radioactive Isotopes

Radioactivity