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radiation

Radiation is energy that travels in the form of waves or particles and is part of our everyday environment. People are exposed to radiation from cosmic rays, as well as to radioactive materials found in the soil, water, food, air and also inside the body. Human-made radiation sources are widely used in medicine, industry, and research.

Learning Objectives: 

What is radiation? 

Radiation is energy that comes from a source and travels through space in the form of waves, rays or particles. This energy has an electric field and a magnetic field associated with it and has wave-like properties. You could also call radiation “electromagnetic waves”.

This method of energy transfer does not rely upon any contact between the energy source and the object as is the case with conduction and convection. Also, when the transfer of energy happens by radiation, there is no conductive medium (such as in space). That lack of medium means there is no matter there for the heat to pass through. No mass is exchanged and no medium is required in the process of radiation. 

Energy and radiation

Radiation is energy in movement.

Types of radiation

There are two main types of radiation: Non-ionizing radiation and Ionizing radiation

Ionizing radiation is a type of energy released by atoms that travels in the form of electromagnetic waves (gamma or X-rays) or particles (neutrons, beta or alpha). Ionizing radiation can remove electrons from the atoms, i.e. they can ionize atoms. 

Ionizing radiation is short-wavelength/high frequency higher energy.

In terms of natural radiation sources, there are more than 60 different naturally occurring radioactive materials present in the environment, with radon gas being the highest contributor to people’s exposure.

There are three types of ionizing radiation: 

Alpha (α) radiation  These are positively charged and made up of two protons and two neutrons from the atom’s nucleus. Even though alpha particles are very energetic, they are so heavy that they use up their energy over short distances and are unable to travel very far from the atom. They can be stopped by the skin. Particles entering the body through food or lungs can be dangerous. 
Beta (β) radiation  are small, fast-moving particles with a negative electrical charge that are emitted from an atom’s nucleus during radioactive decay. Beta particles are more penetrating than alpha particles, but are less damaging to living tissue and DNA because the ionizations they produce are more widely spaced. They travel farther in air than alpha particles, but can be stopped by a layer of clothing or by a thin layer of a substance such as aluminum.
Gamma  (γ) radiation  These are weightless packets of energy called photons. Unlike alpha and beta particles, which have both energy and mass, gamma rays are pure energy. Gamma rays are similar to visible light, but have much higher energy. They are a radiation hazard for the human body. Gamma rays can pass completely through the human body; as they pass through, they can cause ionizations that damage tissue and DNA.

Ionizing Radiation has sufficient energy to produce ions in matter at the molecular level. If that matter is a human significant damage can result including damage to DNA and denaturation of proteins. This is not to say that non-ionizing radiation can’t cause injury to humans but the injury is generally limited to thermal damage i.e. burns.

The following illustration shows how electromagnetic radiation interacts with the body: 

 

Examples of radiation in our everyday life

Do you know we are constantly exposed to radiation through various sources in our everyday life? 

 

 

  1. Sun - One of the most important sources of energy is the Sun. The cosmic radiation emitted from the Sun is a mixture of electromagnetic waves; which range from infrared (IR) to ultraviolet rays (UV). In addition, it also emits visible light. Most of the radiation emitted by the Sun is absorbed by the atmosphere. However, the part which is not absorbed by the atmosphere reaches the earth. Humans are exposed to this part of the radiation almost all time.
  2. Burner - While boiling water or cooking food, you are yet again exposed to radiation. The visible sign of radiation is when you heat up a substance as much as you can, say, for example, heating a stove for a long time will make it glow red. This is a visible sign of radiation. However, even if it is visibly not glowing, then also it radiates heat.
  3. Television - Television has formed one of the most common forms of entertainment in the past few years. Television, too, emits radiation. The old television sets emit x-ray waves which can easily be absorbed by the human body, and is harmful as well. However, modern TV sets use Liquid Crystal Displays (LCD) or Plasma Displays which are not only less harmful than the older sets but are also incapable of producing x-rays.
  4. Bonfire & candle - Whenever you would have gone camping, you might have had the chance to set up a bonfire and bask along with your friends. While sitting around the campfire, you are exposed to radiations. Same happens when you light a candle. Exposure to fire also leads to exposure to radiations
  5. Medical imaging - There is no doubt that during medical imaging, an individual is exposed to radiations at a high level. During an x-ray, CT, and nuclear imaging, the body’s internal organs and structures are revealed by the penetration of high-energy wavelength or particles.
  6. Stereo - Radio waves are most commonly used in communication. Television, cell phones, and radios utilize radio waves and, in turn, convert them into vibrations so that sound waves can be created. The artificial sources of radio waves include electrical generators, power lines, appliances and radio transmitters.
  7. Oven - To heat food in a microwave oven, high levels of radiation are employed. Food in the microwave oven is heated when microwaves are absorbed by the water content present in the food. Absorption of the microwaves causes water molecules to vibrate and, hence, produce heat.
  8. Mobile phones - This might not come as a surprise for you that mobile phones emit non-ionizing radiations from their antennas. Exposure to radio-frequency radiation causes heating of the area of the body where a mobile phone is being held like near the ear. However, the amount of heat radiated is not sufficient to increase the temperature of the body.
  9. Wifi Router - With the advancement in technology, wifi routers have found their way in each and every household. There can be no denying the fact that wifi has become an important part of our daily life. However, you might be surprised to know that the wifi routers also emit electromagnetic radiations. The exposure to such electromagnetic radiations can also have consequences on human health.
  10. Laser beam - Light Amplification Stimulated Emission of Radiation (LASER) also produces radiation. The exposure to laser has often been the cause of temporary blindness, disorientation, and headaches. However, lasers have found widespread uses in printing, optics, DNA sequencing, medicine and surgery, and laser cutting.

Blackbody Radiation

A blackbody is defined as a perfect emitter and absorber of radiation. At a specified temperature and wavelength, no surface can emit more energy than a blackbody. A blackbody is a diffuse emitter which means it emits radiation uniformly in all directions. Also, a blackbody absorbs all incident radiation regardless of wavelength and direction.

Difference between Radiation and Radioactivity

Radiation is the release of energy, whether it takes the form of waves or particles. Radioactivity refers to the decay or splitting of an atomic nucleus. A radioactive material releases radiation when it decays. Examples of decay include alpha decay, beta decay, gamma decay, neutron release, and spontaneous fission. All radioactive isotopes release radiation, but not all radiation comes from radioactivity.

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