What is Microwave?
Microwaves attract all the attention when it comes to making our lives simpler in terms of cooking food. This article covers the properties of the microwave and also its production. We will also be discussing the difference between radio waves and microwaves. If you encounter any doubts while reading this article then the frequently asked questions at the end may help you out with those.
Microwaves are electromagnetic radiation as are ultraviolet radiation X rays, gamma rays, and radio waves. Microwaves have a range of applications including radar communications and best known by most people, cooking.
During primitive days, ancestors used wood, coal to cook their food. With the evolution of human beings, the cooking style also changed, and people started using LPG. Today, in modern times, we have significantly evolved with technology and use microwave radiation for cooking food quickly at our convenience.
So, let’s understand microwave radiation. Microwave radiations are electromagnetic radiations with a frequency range of 300 Mhz – 300 GHz. The wavelength of the microwave spectrum range is between 1 mm to 30 cm. These radiations are often called a microwave. In the electromagnetic spectrum, the microwave is present between infrared and radio waves. With this understanding, let us learn the characteristics of microwaves.
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Properties of Microwaves
Microwaves are reflected by metal surfaces.
They pass through glass and plastics.
They can pass through the atmosphere. Thus, microwaves are used phenomenally in information transmission back and forth to the satellite. It is why satellite dishes are composed of metal content as metal reflects the microwave radiation.
Water absorbs a particular frequency of microwaves. This feature of microwaves is utilized in cooking food. Microwaves are absorbed by the water content present in food, which in turn heat the food. By heating, the atoms and molecules of water in food start vibrating. As a result, the temperature of the food increases, and the food is cooked.
Microwave transmission is affected by wave effects like reflection, refraction, diffraction, and interference.
The time for which the material is exposed to the radiation intensity determines the amount of heating.
Microwaves are reflected by the conducting surfaces and travel in a straight line.
They radiate electromagnetic energy with a shorter wavelength.
The most suitable for the radar systems that are used in aircraft navigation due to their shorter wavelength.
How are Microwaves Produced?
Microwaves are generated by vacuum tubes devices. These devices work on the ballistic movement of electrons operated by either magnetic or electric fields. There are a few examples of microwave emitters like cavity magnetron, the klystron, the traveling-wave tube(TWT), and many more. These instruments work based on clumps of electrons flying ballistically through them, instead of using a constant flow of electrons. Lower power microwaves can be produced by some solid-state devices such as the FET (field effect transistor), the tunnel diode, the Gunn diode, and the IMPATT diode.
Production of Microwaves
Microwaves are produced by special vacuum tubes like the klystron, magnetron, and Gunn diode.
The frequency of microwaves is selected to match the resonant frequency of motor wall equals so that the energy is transferred efficiently to the kinetic energy of the molecules.
(a) Associated with the greenhouse effect.
(b) and also in remote switches of electrical appliances.
Radio Waves v/s Microwaves
Fun Facts
Did you ever think that we use a plastic or glass container in a microwave oven and not metal containers to heat or cook food? It is because the metal is microwave reflectors. On the other hand, glass and plastic allow the microwave to pass through them.
It is very commonly believed that a microwave is not suitable for health as it emits radiation. Nevertheless, there is a point to note that microwaves use the electromagnetic spectrum at low frequencies. Hence microwave radiations have low energy. Due to this insufficient energy, microwave radiations are not capable of changing the food substance chemically via ionization.
Microwaves traversed through the atmosphere will be absorbed by water. This process is utilized by the weather department to monitor rain. If weak signals are reaching the detector, microwaves have passed through more rain. It helps in the analysis of rainfall. The weaker the signal reaching the detector, the more rain has passed through the microwave radiation
Conclusion
This is all about microwaves, their properties, production, and uses. Focus on its features and find out the difference between microwaves and other radiation waves. Understand how it is being used in different aspects of our modern lives.
FAQs on Microwaves
1. What are microwaves in Physics?
Microwaves are a type of electromagnetic radiation that fall between infrared radiation and radio waves in the electromagnetic spectrum. They have a frequency range of approximately 300 MHz to 300 GHz and a corresponding wavelength from 1 millimetre to about 30 centimetres. Their unique properties make them useful for both communication and heating applications.
2. Where are microwaves placed in the electromagnetic spectrum?
In the electromagnetic spectrum, microwaves are located right between infrared waves and radio waves. This position gives them properties of both; like radio waves, they can pass through the atmosphere for communication, and their energy is high enough (though lower than infrared) to be efficiently absorbed by water, which is a key principle in microwave ovens.
3. What are the key properties of microwaves?
Microwaves exhibit several key properties based on the CBSE/NCERT syllabus:
- They travel in straight lines and can be focused into narrow beams.
- They are reflected by metal surfaces.
- They can pass through materials like glass, plastic, and paper.
- They are absorbed by water, a property used in microwave cooking.
- Like other EM waves, they undergo reflection, refraction, and diffraction.
- They can pass through the Earth's ionosphere, making them suitable for satellite communication.
4. How are microwaves produced?
Microwaves are generated using special vacuum tube devices that operate on the principle of accelerating electrons in a controlled way. The most common high-power generators include the cavity magnetron (used in microwave ovens) and the klystron tube. For lower power applications, solid-state devices like the Gunn diode are used.
5. What are the main applications of microwaves in technology and science?
The primary applications of microwaves include:
- Microwave Ovens: For heating food by exciting water molecules.
- Telecommunications: Used in cellular phone networks, Wi-Fi, and point-to-point data links.
- RADAR (Radio Detection and Ranging): For aircraft navigation, weather forecasting, and detecting the speed of vehicles.
- Satellite Communication: To transmit signals between ground stations and satellites in orbit.
6. How do microwaves heat food, and why are metal containers not used in a microwave oven?
Microwaves heat food by emitting radiation at a frequency that is strongly absorbed by water molecules present in the food. This absorption of energy causes the water molecules to vibrate rapidly, increasing their kinetic energy, which manifests as heat. The heat then spreads throughout the food via conduction. Metal containers are not used because metals reflect microwaves. This reflection prevents the food from heating up and can cause electrical arcs, potentially damaging the oven's internal components like the magnetron.
7. What is the main difference between microwaves and radio waves?
The main difference between microwaves and radio waves lies in their wavelength and frequency. Microwaves have a shorter wavelength and a higher frequency compared to radio waves. This higher frequency allows microwaves to carry more information (higher bandwidth), making them ideal for high-speed data transmission. Their shorter wavelength also allows them to be directed in narrow beams, which is useful for RADAR and point-to-point satellite links.
8. Why are microwaves particularly suitable for satellite communication and RADAR systems?
Microwaves are ideal for these technologies for two key reasons:
- For Satellite Communication: Their short wavelength allows them to easily penetrate the Earth's ionosphere without being reflected or significantly absorbed, ensuring a clear signal path to and from satellites.
- For RADAR Systems: Their short wavelength means they can be reflected off small objects like aircraft and raindrops. This provides high-resolution imaging and precise detection, which is crucial for navigation and weather tracking.
9. Do microwaves cook food from the inside out?
This is a common misconception. Microwaves do not cook food from the 'inside out'. They penetrate the food to a depth of a few centimetres and heat the water molecules in this outer layer. The heat then travels towards the centre of the food via the process of conduction. While this process is faster than in a conventional oven where heat moves from the outside surface inwards, the core of dense food is still cooked last.
10. Why are they called 'microwaves' if their wavelength is measured in centimetres?
The term 'microwave' is a historical one, named relative to the radio waves that were in common use at the time of their discovery. Radio waves have very long wavelengths, often measured in metres or even kilometres. In comparison, the newly discovered waves with wavelengths in the centimetre range were significantly smaller or 'micro'. So, the name refers to their wavelength being 'micro' in comparison to radio waves, not because their size is on the micrometre scale.
