Radiation was first detected by a French scientist Henry Becquerel, who was conducting an experiment with photographic plates. He found that elements like uranium, thorium and potassium emitted certain rays, which had an affect on living beings, vary drastically. There are diferent sources of radiations and their affect on living beings, vary drastically. There are is inherent in the planet's atmosphere, and living beings have an in-built mechnanism to deal with it. While other sources of radiation are activities like nuclear fisson and fusion.
Radiation consists of three types of rays, each with a different capacity to penetrate bodies. These are alpha, beta and gamma rays. Radiation is not harmful in all cases. In face, some types of radiations are unavoidable, like cosmic radiation which originates from stars. The Sun too, radiates cosmic energy produced by nuclear reactions on its surface, consisting of short wavelength emissions of electrons and neutrons. A lead object, one inch thick, can be easily penetrated by such radiations. Thus, you can have an idea about the easily penetrated by such radiations. Thus, you can have an idea about the effect, cosmic radiations can have on living beings. As you you move upwards from this radiation goes on increasing. Therefore, frequent fliers and astronauts are more exposed to cosmic radiation than others.
Ionizing Radiation is invisible and passes through matter. Ionizing radiation like x-rays and gamma rays all the time for medical purposes. However, large doses of ionizing radiation passing through living tissue can affect natural biological processes. Exposure to large doses can be very harmful to one’s health.
 Harmful Effects
Overexposure to these radiations, can alter the DNA of animals by the ionizing effect, it produces. If the rate of ionization is significantly large, it can result in permanent damage of the tissues. Sunburn, melanoma or different types of cancers are caused by overexposure to nuclear radiations from the sun pr nuclear tragedies. Kinetic energy released due to the highly penetrating shock waves generated by a nuclear explosion or the use of nuclear weapons, triggers a thermal radiation. Burns, are the most immediate and primary effects of these radiations.
Thermal radiation is approximately 35-45% of the total energy released in a nuclear explosion or test. This is a sufficiently large quantity, to permanently alter the gene structure and introduce hereditary problems, as is evident from the bombings of Hiroshima and Nagasaki. The subsequent generations were found to have several abnormalities. There is a parameter called radiation absorbed dose (rad), that give an idea about the effects of radiation that bombards a human body. 50 to 150 rad causes alterations in the blood with symptoms like nausea, fatigue and vomiting. In case of exposure between 150-1100 rad amount, if not treated immediately, a victim may die central nervous system of the body fails, and loses control over all bodily functions, and death may occur in matter of few days or even hours.
 Radiation in Medicine
The following can be certain positive effects of radiation.
- Radio therapy (for treatment of cancers) and X-rays employ controlled exposure to radiation.
- Radio carbon dating is another application, where nuclear radiations are used to determine the properties and uses of several radioactive elements, and also determines the age of fossil samples.
- Sterilization of medical equipment, food and detecting malfunctioning body parts can also be achieved through a limited exposure to radiation.
Radiation, like many other scientific discoveries, can be put to both constructive and destructive uses. It is the responsibilty of humanity to use this powerful tool for benefit of nature and all of its elements.
 Nuclear Meltdown
When a nuclear power plant malfunctions, unchecked nuclear reactions can cause the radioactive material and its container to heat up and melt. The material may escape into the surrounding environment if the containment structure has been damaged.
The resulting danger from a nuclear meltdown is exposure to the environment of radioactive material, but not a nuclear explosion.
 Measuring Radiation
The unit sievert (Sv) specifically measures absorbed radiation which is absorbed by a person. Frequently used SI multiples are the millisievert (mSV) (1 mSv = 10−3 Sv = 0.001 Sv)
|20,000 mSv||Cognitive impairment, convulsions and death within hours of exposure|
|10,000 mSv||Internal bleeding, death within 2 weeks of exposure|
|6,000 mSv||Typical dosage recorded in Chernobyl workers who died within a month|
|3,000 mSv||Fifty percent chance of survival after exposure|
|700 mSv||Vomiting within hours of exposure|
|100 mSv||If exposed there is an increase incidence of cancer|
|10 mSv||Radiation dose of a full body CT Scan|
|6.9 mSv||Radiation dose of a chest CT Scan|
|2.4 mSv||Normal annual dose of exposure|
|0.04 mSv||Mammogram breast x-ray|
|0.01 mSv||Dental x-ray exposure|
 Radiation Poisoning
Also known as Acute radiation syndrome (ARS) is a series of health effects which occur within weeks or months of exposure to high amounts of ionizing radiation.
The onset and type of symptoms that progresses depends on the dose of radiation exposure. Smaller doses of exposure causes nausea and vomiting and symptoms related to falling blood counts such as infection and internal bleeding. Relatively larger doses can result in neurological effects and rapid death. Treatment of acute radiation syndrome is generally supportive with blood transfusions and antibiotics.