Magnetism and magnetic fields Study Guide

Radioactive materials present hazards through two main mechanisms: contamination and irradiation. It's crucial to distinguish between them to implement appropriate safety measures.

Contamination occurs when a radioactive substance is present on or inside an object or a living organism. This means the radioactive atoms themselves have transferred and settled on a surface, in the air, in food, or directly on or within the body. For example, if a radioactive dust particle lands on your skin, you are contaminated. If you ingest radioactive material, internal contamination occurs. The danger of contamination lies in the direct contact of radioactive sources with body tissues, leading to continuous exposure and potential damage as the radioactive nuclei decay and emit radiation directly to nearby cells. Removing contamination often involves physical cleaning, isolation, or medical treatment to expel the radioactive material.

Irradiation, on the other hand, is the exposure to radiation from an external source, but the radioactive material itself is not transferred. Think of it like being exposed to light from a lamp; the light hits you, but you don't become the light source. With irradiation, the body or object simply absorbs energy from the radiation passing through it. For example, standing near a radioactive source exposes you to irradiation, but you do not become radioactive. Once the external source is removed or shielded, the irradiation stops, and the exposed object or person does not retain any radioactivity. The hazard of irradiation depends on the type of radiation, its intensity, the distance from the source, and the duration of exposure. Measures to reduce irradiation include shielding, increasing distance from the source, and limiting exposure time.

The electromagnetic (EM) spectrum is an entire range of waves that travel through space and matter, carrying energy. These waves are distinguished by their wavelengths and frequencies, but they all travel at the speed of light in a vacuum. The spectrum includes, in order of decreasing wavelength and increasing frequency: radio waves, microwaves, infrared radiation, visible light, ultraviolet radiation, X-rays, and gamma rays. Our eyes, however, are biological sensors that are specifically designed to detect only a very small portion of this vast spectrum. This sliver is what we call 'visible light.'

Visible light itself is composed of different colours, each corresponding to a slightly different wavelength: red, orange, yellow, green, blue, indigo, and violet (ROYGBIV). Red light has the longest wavelength within the visible spectrum, while violet light has the shortest. Wavelengths longer than red light are infrared, and our eyes cannot see them. Wavelengths shorter than violet light are ultraviolet, and again, these are invisible to us. This limitation of our vision means that a huge amount of information carried by other parts of the EM spectrum, such as radio signals from space or X-rays used in medical imaging, remains undetectable to the naked eye. Specialized instruments and technologies are needed to detect and interpret these 'invisible' parts of the spectrum, allowing us to understand the universe and observe phenomena that are beyond our natural sensory capabilities.