To understand microwaves and their common uses in technology, one could say they’re produced by wiggling in a magnetic field. They’re easily transmitted through air, hence, they’re used for communication. The right wavelength is absorbed by water, so they’re used for heating food. And finally, with radar, the scattering properties of materials can be used to detect objects flying in the air.
Features of Microwave Radiation
Microwaves include electromagnetic radiation with wavelengths from about a third of a millimeter up to a third of a meter, or about a foot long. That range overlaps with the shortest radio waves, and there’s no clear divide between radio and microwave. Microwave frequencies consequently, because of their length, range from about one billion to about one hundred billion cycles per second.
That’s one to one hundred gigahertz. A gigahertz is a billion cycles per second. Microwaves are produced primarily by a rapid oscillating electrical field or magnetic field, and they find a number of common uses in technologies.
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Microwaves at Home
Probably the most frequent everyday application of microwaves is in microwave ovens. The microwave oven relies on the fact that the water molecules present in all different kinds of food actually absorb microwaves of a particular frequency, 2.45 gigahertz.
When a frequency of 2.45 gigahertz is applied to a water molecule, it starts vibrating rapidly and oscillates at that frequency. So here’s a technology that’s widely used today for heating food, but also it’s used in many different technologies and industries because other wavelengths in microwaves can be used to heat up other kinds of materials.
So, it’s sometimes used to heat up materials in synthetic laboratories and so forth. So microwaves are finding widespread use for heating applications. The effect of heating by microwaves was reportedly discovered by a physicist named Percy Spencer.
How a Microwave Oven Works
The microwave oven is a beautifully designed and very simple device. It has a microwave generator called a magnetron. And a magnetron is a device that simply is designed to oscillate a magnetic field at about two-and-a-half gigahertz. So, this device, which has an oscillator in one portion, then produces microwaves, which are then focused and reflected through a conduit.
The microwave oven has to have two characteristics. The first is that microwaves have to be reflected off the inside surface because if the microwaves pour into the box, they scatter, bounce off, and then are eventually absorbed by the food.
But the outside walls of the microwave have to be opaque to microwaves so they don’t leak out. The other main device in the microwave oven is a magnetron, which merely fits on the side of that box and pumps microwaves into the box. That’s how the microwave oven works.
Learn more about states of matter and changes of state.
Microwaves in Communication
Another important application of microwaves is in communication. Microwaves can be focused on a narrow beam, like a flashlight. They’re not easily scattered by air. Microwaves are used to make secure and point-to-point communication, so people on the side are not able to pick up that transmission.
There is a need to have a direct line of sight with microwave communications. That’s why there are microwave relay towers dotting the countryside. These are tall towers with sort of odd cone-shaped devices, and they point in one direction or another. They link different microwave towers so there’s a communication network of microwave relay stations.
By the way, most cellular phones at one point or another, and also satellite communication, use microwave relays. But handsets can’t have a point-to-point kind of communication, it has to radiate signals in all directions because the person is moving. So, anybody can listen in to the conversation, which is why cell phone conversations are not secure, even though the point-to-point microwave communication is.
How Microwaves are Used to Make a Radar
Radar uses the reflection of microwaves off solid objects. A radar antenna often acts as both the transmitter and the receiver. Microwaves are sent out from that dish, and then they’re reflected back to the dish. Directions, distance, and the velocity of the object can be determined by the radar.
Modern military radar is amazing. It’s so sensitive that it’s said that one can pick up a housefly at a distance of a mile with modern military radar. So, it’s a very sensitive way to pick up the distance, the direction, and the speed of an object.
Radar can be jammed in a number of different ways. One is to simply broadcast a very high-intensity microwave beam, which swamps the radar detector. Another is to drop lots of pieces of shiny metal material, which act as reflectors and confuse the radar because it picks up so many different hits and echoes.
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Stealth Technology against Microwaves
Modern militaries are nowadays working on stealth technology. In the early days, stealth equipment had lots of flat, smooth surfaces, and the flat surfaces acted partly as reflecting mirrors for microwaves. Mirror-like surfaces are one way to achieve a stealth kind of appearance.
The more recent stealth equipment, though, has microwave-absorbing materials, which are much smoother on their surface. And so that works in a slightly different way. In any case, you can imagine some of these stealth fighters have the appearance of a housefly at about a mile. They’re such great radar-absorbing materials and are almost invisible to radar.
Common Questions about Microwaves
Microwaves are widely used today. Some of the uses of microwaves include heating devices, communication devices, and radar.
A microwave oven has two features. The main device of the microwave oven is called a magnetron that oscillates a magnetic field at a specific frequency. This oscillator produces microwaves.
Broadcasting a high-intensity microwave beam can jam radars. Also, shiny objects act as reflectors resulting in radars being jammed.