What are Microwaves – Basics, Applications & Effects

Microwaves are everywhere in current technology, especially in the most popular television industries. We can notice that TV programs are accessible all over the world, so the microwave’s wide wavelength or frequency permits for the transcontinental change of TV content. By using different kinds of complex networks, limited stations get TV signals & immediately transform the signal to a more suitable lower signal. So private TV sets can transmit the preferred content. Microwaves are very famous between local and national security channels. For instance, microwaves are used missile guidance infrastructures to control the speed of their missiles as well as parameters. This article discusses an overview of microwaves.

What are Microwaves?

Microwaves refer to the electromagnetic rays with frequencies between 300MHz and 300GHz in the electromagnetic spectrum. Microwaves are small when compared with the waves used in radio broadcasting. Their range is in between radio waves and infrared waves. Microwaves travel in straight lines and they will be affected lightly by the troposphere. They don’t require any medium to travel. Metals will reflect these waves. Nonmetals such as glass and particles are partially transparent to these waves.

Microwaves are suitable for wireless transmission of signals having larger bandwidth. Microwaves are most commonly used in satellite communications, radar signals, phones, and navigational applications. Other applications where microwaves used are medical treatments, drying materials, and in households for the preparation of food.

Practically a microwave technique tends to move away from the resistors, capacitors, and inductors used with lower-frequency radio waves. Instead, distributed and transmission-line theory is a more useful method for design and analysis. Instead of open-wire and coaxial lines used at lower frequencies, waveguides are using. And lumped elements and tuned circuits are replaced by cavity resonators or resonant lines.

Even at higher frequencies, where the wavelength of the electromagnetic waves becomes small when compared to the size of the structures used to process them, the microwave has become the latest technology, and the methods of optics are used. High-power microwave sources use specialized vacuum tubes to generate microwaves.

How do Microwaves Work?

The generation of Microwaves can be done in the micro-oven with the help of an electron tube known as a magnetron. The microwave signals are reproduced in the inside of the metal in the oven wherever the food absorbs these waves. The Microwave signals in the food can cause water molecules to pulsate, generates heat to cook the food. So foods which have high water content can be very easily cooked like fresh vegetables.

The microwave energy can be changed to warm up the food because this energy is absorbed by food & it does not prepare food contaminated or radioactive. Even though the heat can be generated within the food directly, microwave ovens do not heat food from the inside and outside. Once solid foods are heated, the external layers are heated by microwaves whereas the inside of the food can be heated because of the heat conduction from the burning external layers.

As compared to normal cooking, microwave cooking is more energy efficient because foods heat quicker & the energy will heat the food simple, but not the entire oven box. The food cooking in the microwave does not lessen the nutritional value. Actually, foods in a microwave oven can keep vitamins and minerals, as microwave ovens can heat more rapidly without including water.
In microwave ovens, paper, plastic, glass, ceramic containers are used as microwaves allow these materials

Some plastic material-based containers should not be utilized in ovens as they can be dissolved through the warmth of the inside food. Usually, aluminum foil otherwise metal pans should not be used within an oven, because these materials cause the food to heat unequally & there is a chance to get over the damage. The directions that approach with every microwave oven specify the types of containers to utilize. They also include how to check containers before using them in the ovens.

Properties of Microwaves

The main properties of microwaves include the following.

• These waves move in a straight line to reflect throughout the conducting faces.
• These are simply attenuated in fewer distances.
• These are not replicated through the Ionosphere.
• Microwaves emit electromagnetic energy with fewer wavelengths.
• Microwave currents supply throughout a thin cable layer.
• The microwaves reflect through metal surfaces.
• They flow through plastic or glass
• The transmission of the microwave can be affected through effects of signal like refraction, deflection, interference & diffraction.

Types of Microwaves

Microwaves are available in different types based on the application like the following.

Countertop

Countertop microwaves are a standard as well as a traditional microwave. Its measuring range is from 0.5 cubic feet to above 2. They can arrange on any open face within your kitchen room. These are self-supported so easily movable.

• The power can capacity ranges are wide
• The countertop model size ranges from 18-24 inches large, 10-18 inches high &18-22 inches deep.
• These are reasonable including functionality and flexible features

Over-the-Range

These types of microwaves are arranged cooktop in the position of a variety hood. The function of this microwave is similar to countertop type, however, it removes steam, smoke & cooking smells using an inbuilt airing system.

• It includes a sensor cook feature so that the food can reheat
• The width of these microwaves ranges from 29-30 inches, 16-18 inches in height & 15to 16 inches in depth.
• As compared to the conventional type, these microwaves are shorter slightly.
• It includes an inbuilt light to provide brightens for the surface while cooking.
• Different vent options
• These are available in different sizes and ranges

Built-In

These microwaves are arranged into a wall otherwise cupboard to operate conveniently. With a similar capability to other microwave models, the fixed design includes the benefits of saving counter area & allows cooking multiple people together.

• It needs a high upfront investment.
• It requires professional installation.
• These are available in different ranges
• The dimensions of these microwaves are similar to countertop models including similar capacities.

Microwave Drawer

• These are arranged under a wall so that we can pull out similar to a drawer.
• Food can be placed or removed from the top view instead of the front side of the microwave
• These are expensive as compared to other types; they include more features by providing a smooth, trendy look within the kitchen.
• These microwaves are available with security locks to avoid curious children from discovering the machine.
• This kind of microwave drawer is simply easy to operate with a single hand.
• The widths of microwave drawers are available in two sizes; however, the inner measurements are similar whereas the outside width is either 24 inches otherwise 30 inches. Inside dimensions are 7.5 or 16-inches wide, 7.1 or 8 inches high & 16 inches deep otherwise 1.2 cubic feet.

Convection Microwaves

In this kind of microwaves, cooking can be circulated and hot air helps the food to cook evenly. Along with the inside cooking speed, the microwave gives the combined techniques to cook different types of foods very quickly especially baked goods.

• The power ranges from 600 watts to 1300 watts.
• The capacity ranges for the compact size from 0.5 cubic feet to 0.8 cubic feet, for mid-sized ranges from 0.8 cubic feet to 1.4 cubic feet & for large-sized capacity; it ranges from.4 to above 2 cubic feet.
• External dimension ranges, however, offer similar sizes of countertop microwaves.
• Convection microwaves quickly heat food.
• In these microwaves, metal utensils, as well as pans, cannot be utilized

How are Microwaves Produced?

Vacuum tube devices generate Microwaves that function on the ballistic movement of the electron that is controlled through magnetic otherwise electric fields. Some more microwave generators also available like the klystron, the cavity magnetron, the gyrotron, the TWT (the traveling-wave tube).

These kinds of devices mainly work within the mode of density modulated in place of the current modulated mode. Lower power microwaves generate through some solid-state devices like the tunnel diode, the FET, the IMPATT diode & the Gunn diode, etc.

Microwaves play a key role in microwave ovens to keep the food fresh. In these kinds of ovens, the frequency can be selected to equal the water molecule’s resonant frequency so that the energy of these waves can be transferred powerfully like kinetic energy (KE) of water molecules which is transferred through the whole food without wasting energy.

Applications and Uses of Microwave

Most common applications are within the range of 1 to 40 GHz. Microwaves are suitable for wireless transmission (wireless LAN protocol Ex- Bluetooth) signals having higher bandwidth. Microwaves are commonly used in radar systems where radar uses microwave radiation to detect the range, distance, and other characteristics of sensing devices and mobile broadband applications.

Microwave technology is used in radio for broadcasting and telecommunication of transmission because due to their small wavelength, highly directional waves smaller and therefore more practical than they would be at longer wavelengths (lower frequencies) before the introduction of Fiber optic transmission. Microwaves are generally used in telephones for long-distance communication.

Several other applications where microwaves used are medical treatments; microwave heating is used for drying and curing products, and in households for the preparation of food (microwave ovens).

An Application of Microwave

Microwave Oven is commonly used for cooking purposes without using water. The high energy of the microwave rotates the polar molecules of water, fat, and sugars of the foodstuff. This rotation causes friction that results in heat generation. This process is called Dielectric heating. The excitation by the microwave is almost uniform so that the food will heat up uniformly. The cooking in the microwave oven is fast, efficient, and safe.

The microwave oven consists of a high voltage transformer that passes energy into the Magnetron, a Magnetron chamber, a Magnetron control unit, a waveguide, and the cooking chamber. The energy in the microwave oven has a frequency of 2.45 GHz with a wavelength of 12.24 cm. The Microwave propagates as alternating cycles so that the polar molecules (one end positive and the other end negative) align themselves according to the alternating cycles. This self-alignment causes rotation of the polar molecules.

The rotating polar molecules hit other molecules and put them into motion. Microwave-induced heating is more efficient if the tissue has high water content since there are free water molecules to rotate. Fats, sugars, Frozen water, etc show less dielectric heating due to the presence of fewer free water molecules. The microwave cooks the outer part of the food first and then the inner part similar to ordinary cooking using a flame.

The cooking chamber of the microwave oven is a Faraday cage that prevents the microwave to leak out into the environment. The glass door of the oven helps to view the interior of the oven. The Faraday cage, as well as the door, is well protected using conductive mesh to keep the shielding. The perforations in the mesh are lesser in size so the microwave cannot escape through the mesh.

The electrical efficiency of the Microwave oven is high since the oven converts only a portion of the electrical energy. A typical oven consumes 1100 electrical energy to produce 700 watts of microwave energy. The remaining 400 watts are dissipated as heat in the Magnetron. Additional energy is required for operating other components of the oven like a lamp, cooling fan turntable motor, etc.

Microwave Bands

Microwaves are found at the higher end of the radio spectrum, but they are commonly different from radio waves based on the technology using them. Microwaves are divided into sub-bands based on their wavelengths which are providing different information. The frequency bands of microwaves are as follows:

L-Band

L bands are having a frequency range between 1 GHz to 2 GHz and their wavelength in free space is 15cm to 30cm. These ranges of waves are used in navigations, GSM mobile phones, and in military applications. They can be used to measure the soil moisture of rain forests.

S-Band

S-band microwaves are having a frequency range between 2 GHz to 4 GHz and their wavelength range is 7.5cm to 15 cm. These waves can be used in navigation beacons, optical communications, and wireless networks.

C-Band

C band waves are having a range between 4 GHz to 8 GHz and their wavelength is between 3.75 cm to 7.5 cm. C band microwaves penetrate clods, dust, smoke, snow, and rain to reveal the earth’s surface. These microwaves can be used in long-distance radio telecommunications.

X-Band

The frequency range for S-band microwaves is 8 GHz to 12 GHz having a wavelength between 25 mm to 37.5 mm. These waves are used in satellite communications, broadband communications, radars, space communications, and amateur radio signals.

Ku-Band

These waves are occupying the frequency range between 12 GHz to 18 GHz and having a wavelength of between 16.7 mm to 25 mm. “Ku” refers to Quartz-under. These waves are used in satellite communications for measuring the changes in the energy of the microwave pulses and they can determine the speed and direction of wind near coastal areas.

K-Band and Ka-Band

The frequency range for K band waves is between 18 GHz to 26.5 GHz. These waves are having a wavelength between 11.3 mm to 16.7 mm. For the Ka-band the frequency range is 26.5 GHz to 40 GHz and they are occupying the wavelength between 5 mm to 11.3 mm. These waves are used in satellite communications, astronomical observations, and radars. Radars in this frequency range provide short-range, high resolution, and high amounts of data at the renewing rate.

V-Band

This band stays for high attenuation. Radar applications are limited to a short range of applications. The frequency range for these waves is 50 GHz to 75 GHz. The wavelength for these microwaves is between 4.0 mm to 6.0 mm. There are some more bands like U, E, W, F, D, and P having very high frequencies which are used in several applications.

Microwave Radiation and Its Effect on Health

Radiation is an energy that comes from a source and travels through some medium or space. Generally, RF radiation will be produced by several devices like TV and Radio transmitters, induction heaters, and dielectric heaters. Microwave radiation will be produced by radar devices, dish antennas, and microwave ovens.

Due to the microwave radiation, the body temperature may increase. There is a higher risk of heat damage with organs which are having poor temperature control, such as the lens of the eyes. Since radiation energy absorbed by the body varies with frequency, measuring the rate of absorption is very difficult.

Advantages of Microwave Technology

The advantages of microwave technology include the following.

1. It does not require any cable connection.
2. They can carry high quantities of information due to their high operating frequencies.
3. We can able to access more numbers channels.
4. Low-cost land purchase: each tower occupies a small area.
5. High frequency/short wavelength signals require a small antenna.

Disadvantages

The disadvantages of microwave technology include the following.

1. Attenuation by solid objects: birds, rain, snow, and fog.
2. It’s much expensive to build long towers.
3. Reflected from flat surfaces like water and metal.
4. Diffracted (split) around solid objects.
5. Refracted by the atmosphere, thus causing the beam to be projected away from the receiver.

Now you have understood the concept of microwaves and applications and effects from the above article so if you have any queries from the above topic or the electrical and electronic projects leave the comments section below.

Photo Credit:

• Microwave Bands By gstatic
• Wave meter for measuring in the Ku band By gstatic
• Microwave radiation effect after phone call By wikimedia