What is meant by radiation?
Radiation is energy that moves from one place to another.Light,Sound,Heat and X-rays are examples for RADIATIONS.The different kinds of radiation fall into a few general categories as, Electro magnetic radiation , Mechanical radiation , Nuclear radiation and Cosmic rays.
Electro magnetic radiation
Electro magnetic radiation comes from atoms, the building block of all matter.Some of the particles that make up atoms have an electric charge. The motion of these charged particles produces energy that can be described as traveling as waves. These waves combine electricity and magnetism. They can travel through empty space, like in outer space. They can also travel through air and even solid substances , such as glass.Through empty space ,the waves travel at a speed of about 186,282 miles per second [299,792 km per s]
What is meant by wave length
The distance from the crest of one wave to the crest of the next wave is called wave length.you can examine it clearly by looking at the diagram.
What are the types of electromagnetic radiations ?
The types of electro magnetic radiations are radio waves , infrared rays , visible light , ultraviolet rays , X-rays , gamma rays and Radio waves.
Radio waves
Radio waves are used for sending signals , including Television and radio broad casts. Micro waves are short radio waves that can be use to cook food in micro wave ovens.
Visible light
Visible light is all the wave lengths of electro magnetic radiation that the human eye can see . Different wave lengths of visible light are seen in different colors
Gamma rays
Gamma rays are used in medicine to kill cancers
Infrared radiation
Infrared radiation or heat , is given off by warm objects. Infrared radiations from the sun heats Earth .
Ultra violet radiation
Ultra violet radiation is used by the skin to make a nutrient called vitamin D.
X-rays
X-rays are used to make a picture of something inside an object,such as bones inside the body.
Is these radiations are harmful to our body?
Radiations like radio waves , visible light etc are not harmful for our body.Because in these radiations the wave length is longer so the energy it carries is small.but, When the wave lengths are shorter , it carries more energy, so the radiations which has shorter wave lengths would be harmful for our body.So the radiations like Ultra - violet radiations , x- rays and Gamma rays can be harmful to our body.
Mechanical radiation
Unlike electromagnetic radiations mechanical cannot travel through empty spaces. It can travel only through a substance , such as air ,water or solid objects. A common example of mechanical radiation is sound. Sound is produced by the back-and-fourth motion of a vibrating object.This motion produces sound waves that travels from the object.Sound travels more slowly than light does.A earth quake produces another form of mechanical radiation.The shock waves created by an earthquake travel through Earth and cause the ground to shake.
How to prove that sound travels slowly than light?
When lightning occurs. Firstly, we can see a flash of light then secondly, after 2,3 seconds we can hear a sound.So you can conclude easily that sound travels slower than that of light.
Nuclear radiation
Nuclear radiation comes from the nucleus,or center of atoms. It is produced when the nucleus changes in some way .The nucleus of some types of atoms is unstable. An unstable nucleus can naturally change into a another type of nucleus.When it does this , it shoot off nuclear radiation in the form of small particles or gamma rays. Atoms that give off radiations in this way are called radioactive.Nuclear radiation carries a lot of energy, so it can be dangerous.
Cosmic rays
Cosmic rays are a type of radiation made up of tiny parts of atoms that speed through outer space. Cosmic rays come from the sun , but most come from farther away in the galaxy. Some cosmic rays travel almost at the speed of light.Because they move so fast they have very high energy . Scientists study cosmic rays to learn more about the make up of the galaxy.
