1. What Is Radiation?

1. What is Radiation?

This figure illustrates the relative abilities of three different types of ionizing radiation to penetrate solid matter. For other uses, see Radiation (disambiguation). In physics, radiation describes any process in which energy emitted by one body travels through a medium or through space, ultimately to be absorbed by another body. Non-physicists often associate the word with ionizing radiation (e.g., as occurring in nuclear weapons, nuclear reactors, and radioactive substances), but it can also refer toelectromagnetic radiation (i.e., radio waves, infrared light, visible light, ultraviolet light, and X-rays) which can also be ionizing radiation, to acoustic radiation, or to other more obscure processes. What makes it radiation is that the energy radiates (i.e., it travels outward in straight lines in all directions) from the source. This geometry naturally leads to a system of measurements and physical units that are equally applicable to all types of radiation.

2. What are the types of Radiation Ionizing Radiation Some types of radiation have enough energy to ionize particles. Generally, this involves an electron being 'knocked out' of an atom's electron shells, which will give it a (positive) charge. This is often disruptive in biological systems; and can cause mutations and cancer. These types of radiation generally occur in radioactive decay.

Alpha Radiation Alpha (α) decay is a method of decay in large nuclei. An alpha particle (A helium nucleus, He2+), consisting of 2 neutrons and 2 protons, is emitted. Because of the particle's relatively high charge, it is heavily ionizing and will cause severe damage if ingested. However, due to the high mass of the particle,

it has little energy and a low range; typically alpha particles can be stopped with a sheet of paper (or skin).

Beta(+/-) Radiation Beta-minus (β-) radiation consists of a energetic electron. It is less ionizing than alpha radiation, but more so than gamma. The electrons can often be stopped with a few centimeters of metal. It occurs when a neutron decays into a proton in a nucleus; release the beta particle and anantineutrino. Beta-plus (β+) radiation is the emission of positrons. Because these are antimatter particles, they annihilate any matter nearby, releasing gamma photons. Therefore, they pose no direct risk, although the gamma photons released do.

Gamma Radiation Gamma (γ) radiation consists of photons with a frequency of greater than 1019 Hz. Although highly penetrating, the photons are not typically ionizing because of their massless nature. Gamma radiation occurs to rid the decaying nucleus of excess energy once it has emitted either alpha or beta radiation.

Non-ionizing Radiation Non-ionizing (or non-ionising) radiation, by contrast, refers to any type of radiation that does not carry enough energy per quantum to ionizeatoms or molecules. Most especially, it refers to the lower energy forms of electromagnetic radiation (i.e., radio waves, microwaves, terahertz radiation, infrared light, and visible light). The effects of these forms of radiation on living tissue have only recently been studied. Instead of producing charged ions when passing through matter, the electromagnetic radiation has sufficient energy only for excitation, the movement of an electron to a higher energy state. Nevertheless, different biological effects are observed for different types of non-ionizing radiation.[1][2] Electromagnetic Radiation Electromagnetic radiation (sometimes abbreviated EMR) takes the form of self-propagating waves in a vacuum or in matter. EM radiation has an electric and magnetic field component which oscillate in phase perpendicular to each other and to the direction of energy propagation. Electromagnetic radiation is classified into types according to the frequency of the wave, these types include (in order of increasing frequency): radio waves, microwaves, terahertz radiation, infrared radiation, visible light, ultraviolet radiation, X-rays and gamma rays. Of these, radio waves have the longest wavelengths and Gamma rays have the shortest. A small window of frequencies, called visible spectrum or light, is sensed by the eye of various organisms, with variations of the limits of this narrow spectrum. EM radiation carries energy and momentum, which may be imparted when it interacts with matter.

The electromagnetic spectrum

Light Light, or visible light, is electromagnetic radiation of a wavelength that is visible to the human eye (about 400–700 nm), or up to 380–750 nm.[1] More broadly, physicists refer to light as electromagnetic radiation of all wavelengths, whether visible or not.

Thermal Radiation Thermal radiation is the process by which the surface of an object radiates its thermal energy in the form of electromagnetic waves. Infrared radiation from a common household radiator or electric heater is an example of thermal radiation, as is the light emitted by a glowing incandescent light bulb. Thermal radiation is generated when heat from the movement of charged particles within atoms is converted to electromagnetic radiation. The emitted wave frequency of the thermal radiation is a probability distribution depending only on temperature, and for a genuine black body is given by Planck’s law of radiation. Wien's law gives the most likely frequency of the emitted radiation, and the Stefan–Boltzmann law gives the heat intensity.

Black Body Radiation

Black Body Radiation is a common synonym for thermal radiation . It is so-called because the ideal radiator of thermal energy would also be an ideal absorber of thermal energy: It would not reflect any light, and thus would appear to be absolutely black.

3. How does radioation Interact with matter?

The different parts of the electromagnetic spectrumhave very different effects upon interaction with matter. Starting with low frequency radio waves, the human body is quite transparent. (You can listen to your portable radio inside your home since the waves pass freely through the walls of your house and even through the person beside you!) As you move upward throughmicrowaves and infrared to visible light, you absorb more and more strongly. In the lower ultraviolet range, all the uv from the sun is absorbed in a thin outer layer of your skin. As you move further up into the x-ray region of the spectrum, you become transparent again, because most of the mechanisms for absorption are gone. You then absorb only a small fraction of the radiation, but that absorption involves the more violent ionization events. Each portion of the electromagnetic spectrum has quantum energies appropriate for the excitation of certain types of physical processes. The energy levels for all physical processes at the atomic and molecular levels are quantized, and if there are no available quantized energy levels with spacings which match the quantum energy of the incident radiation, then the material will be transparent to that radiation, and it will pass through.

4. What are the biological effects of radiation? EFFECTS OF RADIATION ON CELLS Biological effect begins with the ionization of atoms. The mechanism by which radiation causes damage to human tissue, or any other material, is by ionization of atoms in the

material. Ionizing radiation absorbed by human tissue has enough energy to remove electrons from the atoms that make up molecules of the tissue. When the electron that was shared by the two atoms to form a molecular bond is dislodged by ionizing radiation, the bond is broken and thus, the molecule falls apart. This is a basic model for understanding radiation damage. When ionizing radiation interacts with cells, it may or may not strike a critical part of the cell. We consider the chromosomes to be the most critical part of the cell since they contain the genetic information and instructions required for the cell to perform its function and to make copies of itself for reproduction purposes. Also, there are very effective repair mechanisms at work constantly which repair cellular damage - including chromosome damage. The following are possible effects of radiation on cells: Cells are undamaged by the dose Ionization may form chemically active substances which in some cases alter the structure of the cells. These alterations may be the same as those changes that occur naturally in the cell and may have no negative effect. Cells are damaged, repair the damage and operate normally Some ionizing events produce substances not normally found in the cell. These can lead to a breakdown of the cell structure and its components. Cells can repair the damage if it is limited. Even damage to the chromosomes is usually repaired. Many thousands of chromosome aberrations (changes) occur constantly in our bodies. We have effective mechanisms to repair these changes. Cells are damaged, repair the damage and operate abnormally If a damaged cell needs to perform a function before it has had time to repair itself, it will either be unable to perform the repair function or perform the function incorrectly or incompletely. The result may be cells that cannot perform their normal functions or that now are damaging to other cells. These altered cells may be unable to reproduce themselves or may reproduce at an uncontrolled rate. Such cells can be the underlying causes of cancers. Cells die as a result of the damage If a cell is extensively damaged by radiation, or damaged in such a way that reproduction is affected, the cell may die. Radiation damage to cells may depend on how sensitive the cells are to radiation. All cells are not equally sensitive to radiation damage. In general, cells which divide rapidly and/or are relatively non-specialized tend to show effects at lower doses of radiation then those which are less rapidly dividing and more specialized. Examples of the more sensitive cells are those which produce blood. This system (called the hemopoietic system) is the most sensitive biological indicator of radiation exposure.

5. What are atoms/ molecules? Atoms are the basic building blocks of matter that make up everyday objects. A desk, the air, even you are made up of atoms. There are 90 naturally occurring kinds of atoms. Scientists in labs have been able to make about 25 more. A molecule is the smallest particle in a chemical element or compound that has the chemical properties of that element or compound. Molecules are made up ofatom s that are held together by chemical bonds. These bonds form as a result of the sharing or exchange of electron s among atoms.

The atoms of certain elements readily bond with other atoms to form molecules. Examples of such elements are oxygen and chlorine. The atoms of some elements do not easily bond with other atoms. Examples are neon and argon. Molecules can vary greatly in size and complexity. The element helium is a one-atom molecule. Some molecules consist of two atoms of the same element. For example, O 2 is the oxygen molecule most commonly found in the earth's atmosphere; it has two atoms of oxygen. However, under certain circumstances, oxygen atoms bond into triplets (O 3 ), forming a molecule known as ozone. Other familiar molecules include water, consisting of two hydrogen atoms and one oxygen atom (H 2 O), carbon dioxide, consisting of one carbon atom bonded to two oxygen atoms (CO 2 ), and sulfuric acid, consisting of two hydrogen atoms, one sulfur atom, and four oxygen atoms (H 2 SO 4 ).

6. What are isotopes? An isotope is a variant on a basic element, a substance made of atoms with a different number of neutrons than is typical. Except for hydrogen, every atomicnucleus in normal matter is made of both protons and neutrons; the only question is how many of each there are. Typically, the number of protons and neutrons is the same. In an isotope, this balance is frequently broken. For example, 238U, the most common state of uranium, has three more neutrons than 235U, the form used in nuclear weapons. A lack of necessary neutrons makes a nucleus unstable. Protons in the nucleus are positively charged, meaning they repel each other. The presence of neutrons is necessary to separate these protons slightly, making the configuration stable. When the configuration is unstable, nuclear decay can result, turning the atoms into showers of radioactive particles. The rate at which the isotope decays is given by its half-life, the interval after which half of the material breaks down. Half-life varies between a fraction of a second and many times longer than the age of the universe. Some isotopes, likeHelium-3, are not radioactive. Besides the occasional tendency to be radioactive, an isotope tends to behave similarly to the natural element it is a variant on. Isotopes can participate in all the same reactions and have approximately the same mass, except in rare cases. Sometimes, their increased mass means that chemical reactions in which they participate are slightly slower than usual. There are many hundreds of known isotopes, and probably hundreds more that we haven’t discovered or produced yet. The most famous isotope is 235U, because of its use in nuclear energy and weaponry. “Enriched” uranium is uranium with a higher concentration of this isotope, while “depleted” uranium has a much lower concentration. An isotopethat is only slightly radioactive can be used as an atomic marker in medical applications, for example to track the spread of a drug in the body. Carbon-14, which comprises a trace amount of all carbon on earth, is a radioactive isotope with concentration levels that can be used to determine the precise age of an artifact or fossil. Helium-3, thought to exist in large quantities on the moon, is among the most promising long-term fuels for fusion power reactors. However, utilizing it effectively will require first mastering other forms of fusion.

7.

What are the radioactive waves?

8. What are the beneficial use of isotopes? Radioactive and stable isotopes are used throughout the world and in many sectors, including medicine, industry, agriculture and research. In many applications isotopes have no substitute, and in most others they are more effective and cheaper than alternative techniques or processes.

9.

Do radio isotopes remain unstable or radioactive all the time?

Most isotopes are stable. Unless disturbed by powerful outside forces, the configuration of the nucleus will remain unchanged indefinitely. Some isotopes, however, are unstable, and will spontaneously decay into a new nuclear configuration. Such isotopes are called radioactive isotopes. Unstable isotopes undergo radioactive decay. Decay involves nuclear reactions in which fundamental changes occur to the nucleus of each atom which decays. There are four basic types of radioactive decay, three of which are useful in the study of the earth. You should be able to describe and distinguish alpha decay, beta decay and electron capture, and determine the daughter products from each type of decay.

10.Give some scientist that make contribution in the development of study in radiation. Wilhelm Röntgen is credited with the discovery of X-Rays. When experimenting with a vacuum and a Crooke's tube, he noticed a phosphorescence on a nearby plate of coated glass. While working with various isotopes ofhydrogen, namely tritium, he found a drastic change in photonic emissions when measuring electrical charges in a vacuum. When he took pictures of the tritium, he found that the state of one solid piece would deteriorate quickly. In one month, he discovered the main properties of Xrays that we understand to this day. Henri Becquerel found that uranium salts caused fogging of an unexposed photographic plate, and Marie Curie discovered that only certain elements gave off these rays of energy. She named this behavior radioactivity. In December 1899, Marie Curie and Pierre Curie discovered radium in pitchblende. This new element was two million times more radioactive than uranium, as described by Marie.

Submitted by: Stephanie S. Masalta Jemflor Ann Imperial Sarah Joy Arduo