UNIT 2 RADIATION

1. WARMING UP

1.1. You are going to read a text about radiation. Before you read, look at the picture. What does it tell you about it?

2. Reading

2.1. Pre-reading tasks

1. Study and learn the following structures

• The nuclei of these atoms are very “neutron rich” which makes emission of the alpha particle possible.

• Like all forms of electromagnetic radiation, the gamma ray has no mass and no charge.

• But unlike light, these rays have great penetrating power and can pass through almost everything

• . The gamma ray is identical in nature to light or microwaves, but of very high energy. (These radiations are of such high energy that when they interact with materials, they can remove electrons from the atoms in the material.)

• It takes very, very thick concrete, lead or steel to block gamma rays.

• It is important to note that there is no such thing as a “pure” gamma emitter.

2. Read the following key-terms. Try to explain their meaning. Use the dictionary if necessary.

radiation, background radiation, radioactivity, radioactive decay, x-rays, gamma rays, alpha particle, beta particle, penetrating power, electromagnetic radiation.

2.2. Read and translate the article

Radiation all around us.

Radiation is everywhere and it is a natural part of our everyday lives. It is a form of energy and a possible consequence of many processes, not just radioactivity. Humans have been exposed to radiation from natural sources since the dawn of time. The sources include the ground we walk on, the air we breathe, the food we eat and the solar system on the whole. About 80% of background radiation originates from naturally occurring sources, with the remaining 20% resulting from man-made sources. Radiation is the term given to a travelling particle or wave and can be split into three main types:

1. Non-ionizing radiation: essentially the low-energy parts of the electromagnetic spectrum. This includes all the light you see, radio waves (also known as microwaves – as in the oven) and infrared (“heat” radiation).

2. Ionizing: radiation that can remove an electron from its orbital

3. Neutrons: free neutron particles that can collide with other atoms.

Non-ionizing radiation is mostly damaging in obvious ways. Alternatively, ionizing radiation can be less obvious but can create damage. Ionizing radiation falls into two main forms: high-energy electromagnetic radiation, including X-ray and gamma rays and particle radiation- alpha and beta particles. These different forms of ionizing radiation differ in their capacity to do damage and their ability to penetrate materials.

Radiation is released during radioactive decay. The radiation emitted may be in the form of particles, such as neutrons, alpha particles, and beta particles, or waves of pure energy, such as gamma and X-rays.

Alpha particle is the nucleus of a helium atom and consists of two protons and two neutrons. Alpha particles are doubly charged (arising from the charge of the two protons). This charge and the relatively slow speed and high mass of alpha particles mean that they interact more readily with matter than beta particles or gamma rays and lose their energy quickly. They therefore have little penetrating power and can be stopped by the first layer of skin or a sheet of paper. But inside the body they can inflict more severe biological damage through inhalation or swallowing than other types of radiation.

Alpha decay is a radioactive process in which a particle is ejected from the nucleus of a radioactive atom and only occurs in very heavy elements such as uranium, thorium and radium. The nuclei of these atoms are very “neutron rich” (i.e. have a lot more neutrons in their nucleus than they do protons) which makes emission of the alpha particle possible.

B eta particles are fast-moving electrons ejected from the nuclei of many kinds of radioactive atoms. Each beta particle carries one electronic unit of negative charge. These particles are lighter and ejected at a much higher speed than alpha particles. They can penetrate up to 1 to 2 centimeters of water or human flesh. They can be stopped by a sheet of aluminium a few millimeters thick.

Beta decay is a radioactive process in which an electron is emitted from the nucleus of a radioactive atom. Like alpha decay, beta decay occurs in isotopes which are “neutron rich”. Atoms which undergo beta decay are located below the line of stable elements on the chart of the nuclides, and are typically produced in nuclear reactors.

G amma rays like light represent energy transmitted in a wave without the movement of material, just like heat and light. Like all forms of electromagnetic radiation, the gamma ray has no mass and no charge. Gamma rays interact with material by colliding with the electrons in the shells of atoms. Gamma rays and X-rays are virtually identical except that X-rays are produced artificially rather than coming from the atomic nucleus. X-rays and gamma rays are penetrating, ionizing radiation and are essentially the same thing. (The difference in terminology is usually that gamma rays come from nuclear decay, while X-rays come from electron orbitals.)

The gamma ray is identical in nature to light or microwaves, but of very high energy. But unlike light, these rays have great penetrating power and can pass through almost everything. It takes very, very thick concrete, lead or steel to block gamma rays. This type of radiation is dangerous and damaging.

It is important to note that there is no such thing as a “pure” gamma emitter. Gamma emitters are associated with alpha, beta, and positron decay.