Where is em radiation made

Examples of stored or potential energy include batteries and water behind a dam. Objects in motion are examples of kinetic energy. Charged particles—such as electrons and protons—create electromagnetic fields when they move, and these fields transport the type of energy we call electromagnetic radiation, or light.

Mechanical waves and electromagnetic waves are two important ways that energy is transported in the world around us. Waves in water and sound waves in air are two examples of mechanical waves.

Mechanical waves are caused by a disturbance or vibration in matter, whether solid, gas, liquid, or plasma. Matter that waves are traveling through is called a medium. Water waves are formed by vibrations in a liquid and sound waves are formed by vibrations in a gas air. These mechanical waves travel through a medium by causing the molecules to bump into each other, like falling dominoes transferring energy from one to the next.

Sound waves cannot travel in the vacuum of space because there is no medium to transmit these mechanical waves. Electricity can be static, like the energy that can make your hair stand on end. Magnetism can also be static, as it is in a refrigerator magnet. A changing magnetic field will induce a changing electric field and vice-versa—the two are linked. These changing fields form electromagnetic waves. Electromagnetic waves differ from mechanical waves in that they do not require a medium to propagate.

This means that electromagnetic waves can travel not only through air and solid materials, but also through the vacuum of space. In the 's and 's, a Scottish scientist named James Clerk Maxwell developed a scientific theory to explain electromagnetic waves.

He noticed that electrical fields and magnetic fields can couple together to form electromagnetic waves. He summarized this relationship between electricity and magnetism into what are now referred to as "Maxwell's Equations.

Heinrich Hertz, a German physicist, applied Maxwell's theories to the production and reception of radio waves. The electromagnetic EM spectrum is the range of all types of EM radiation. The other types of EM radiation that make up the electromagnetic spectrum are microwaves , infrared light , ultraviolet light , X-rays and gamma-rays. You know more about the electromagnetic spectrum than you may think. The image below shows where you might encounter each portion of the EM spectrum in your day-to-day life.

Radio: Your radio captures radio waves emitted by radio stations, bringing your favorite tunes. Radio waves are also emitted by stars and gases in space.

Microwave: Microwave radiation will cook your popcorn in just a few minutes, but is also used by astronomers to learn about the structure of nearby galaxies. Infrared: Night vision goggles pick up the infrared light emitted by our skin and objects with heat. In space, infrared light helps us map the dust between stars. Visible: Our eyes detect visible light. Fireflies, light bulbs, and stars all emit visible light. Ultraviolet: Ultraviolet radiation is emitted by the Sun and are the reason skin tans and burns.

X-ray: A dentist uses X-rays to image your teeth, and airport security uses them to see through your bag. Hot gases in the Universe also emit X-rays.

Gamma ray: Doctors use gamma-ray imaging to see inside your body. Neon signs are other colors, but that is because they are made out of colored glass. The reason why neon signs are a certain color is because when a gas is excited by electricity, it tends to only emit certain colors. If we take a neon sign and separate out the colors with a prism we would see the following spectrum:.

An observant student might now ask -- I see how light can produce colors now, but where does white light come from? The answer is that it comes from all the colors. When you take all the colors and combine them then you will get white. If we place sunlight or light from an incandecent lightbulb though a prism we would see the following spectrum:. Now this spectrum looks different from the neon light because it is continuous.

It is an entire band of light and not just several different lines. The relationship between E and B is shown at one instant in Figure 2a. As the current varies, the magnetic field varies in magnitude and direction. Figure 2. The current I produces the separation of charge along the wire, which in turn creates the electric field as shown. The magnetic field lines also propagate away from the antenna at the speed of light, forming the other part of the electromagnetic wave, as seen in Figure 2b.

The magnetic part of the wave has the same period and wavelength as the electric part, since they are both produced by the same movement and separation of charges in the antenna. The electric and magnetic waves are shown together at one instant in time in Figure 3. The electric and magnetic fields produced by a long straight wire antenna are exactly in phase.

Note that they are perpendicular to one another and to the direction of propagation, making this a transverse wave. Figure 3. A part of the electromagnetic wave sent out from the antenna at one instant in time. The electric and magnetic fields E and B are in phase, and they are perpendicular to one another and the direction of propagation. For clarity, the waves are shown only along one direction, but they propagate out in other directions too.

Electromagnetic waves generally propagate out from a source in all directions, sometimes forming a complex radiation pattern. A linear antenna like this one will not radiate parallel to its length, for example. The wave is shown in one direction from the antenna in Figure 3 to illustrate its basic characteristics.

Instead of the AC generator, the antenna can also be driven by an AC circuit. In fact, charges radiate whenever they are accelerated. But while a current in a circuit needs a complete path, an antenna has a varying charge distribution forming a standing wave , driven by the AC. The dimensions of the antenna are critical for determining the frequency of the radiated electromagnetic waves.

This is a resonant phenomenon and when we tune radios or TV, we vary electrical properties to achieve appropriate resonant conditions in the antenna.

Electromagnetic waves carry energy away from their source, similar to a sound wave carrying energy away from a standing wave on a guitar string.

An antenna for receiving EM signals works in reverse.