Further Research
TYPICAL WAVELENGTH 10-10m (a ten thousand millionth of a metre) i.e. 100,000,000 waves per centimetre.
SOURCES - X-ray tubes
HAZARD - Severe
DETECTOR - Photographic film
USES
- Medical - Identification of damage to bones, destruction of diseased tissue.
- Industrial - Detection of flaws in machines.
BACKGROUND - Sources of x-rays
X-rays are produced whenever high energy electrons impact with a target - so small quantities are produced by cathode ray tubes and television tubes. They have short wavelengths (high frequencies) so can penetrate matter which is opaque to visible light.
Uses of x-rays
Medical uses
1. Diagnosis
Most people are aware that broken bones can be identified by x-rays. The damaged part of the body is exposed to x-rays from a machine and a photographic film is placed on the side behind the injury. Only a very short burst of radiation is passed through the body. This radiation passes through soft tissue with little being absorbed but the denser bones absorb most of it. These latter areas produce a "white image" on the film. If soft tissue is to be investigated, e.g. the kidneys, an x-ray opaque liquid is injected and the flow of this through the system can be followed by taking different pictures after different intervals of time. When necessary moving, instantaneous images can be obtained, e.g. of the digestive system.
2. Treatment
X-ray therapy involves the destruction of diseased tissue by focusing the rays precisely on the tissue, and using a carefully measured dose. Usually a number of beams are used from several directions intersecting at the diseased area to give the correct dose.
Background on x-rays
X-rays were detected towards the end of the 19th century. Since x-rays and cathode rays were produced from the same apparatus, Roentgen, the discoverer thought they might be different forms of the same phenomenon. He later discovered that they were not affected by magnetic fields and had a similar effect as visible light on photographic film. Later studies showed that x-rays could be diffracted by passing them through crystals - this enabled the wavelengths to be measured.
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