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Dr. Tsubokura's Radiation Lecture Vol.33

Author: Masaharu Tsubokura

Editors: Akihiko Ozaki M.D., Yuki Senoo

65. Similar to UV light, the total dose of exposure is a crucial risk factor for radiation-related adverse health outcomes.

Do you know why rainbows have seven colors? Well, to answer this question, we have to first recognize that various kinds of light exist in this world, depending on differences in wavelengths (energy): the color of visible light differs depending on its wavelength. The seven colors in the rainbow (red, orange, yellow, green, blue, indigo and violet) move in different wavelengths.

Human eyes cannot catch all of the wavelengths that exist in the world. Besides visible light, light waves with lower energy (longer wavelengths) are called radio waves and infrared rays, well-known for being produced by fan heaters. In contrast, light waves with higher energy (shorter wavelengths) are called ultraviolet rays; you may be familiar with UV-reducing products. Compared to ultraviolet lights, ionizing radiation (X-rays and gamma rays) have much higher energy.

Radiation is scentless and invisible to human eyes. However, as with ultraviolet radiation, radiation is and always will be present around us, and therefore exposure to radiation is inevitable. However, we should prevent excessive exposure to radiation; the total dose of radiation exposure determines the adverse effects on health. Methods of prevention are the same as for the prevention of UV light exposure.

66. Radioactive substances emit radiation to stabilize their nuclei.

Although it is needless to say, all elements are collections of small invisible matter called atoms.

At the beginning of the 20th century, it was discovered that an atom consists of several pieces of even smaller particles called protons, neutrons, and electrons. For example, a water molecule is composed of 10 protons, 8 neutrons and 10 electrons.

However, when protons, neutrons and electrons are unbalanced, they become incompatible with one another, which makes the substance unstable. This unstable substance is called a radioactive substance.

A cesium 137 atom, often discussed in the media, has four extra neutrons compared to stable cesium.

To stabilize its nucleus, radioactive cesium ejects one neutron or emits energy. This emitted neutron or energy is radiation. After emitting radiation, radioactive substances are balanced and transform into non-radioactive substances.


The Japanese version of the manuscript was originally published in Fukushima Minyu, a local newspaper in Fukushima prefecture, Japan, on April 3rd and 10th 2016 was reproduced for MRIC Global under the author's permission.

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