Microwaves

What is Microwave?

During primitive days, ancestors used wood, coal to cook their food. With the evolution of human beings, a cooking style also changed, and people started using LPG. Today, modern times, we have significantly evolved with technology and use microwave radiations for cooking food quickly at our convenience.

So, let’s understand microwave radiations. Microwave radiations are the electromagnetic radiations with a frequency range of 300Mhz – 300 GHz. The wavelength of the microwave spectrum range is between 1mm 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 the microwaves.

Image will be uploaded soon

Properties of Microwaves

  • The microwave is 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.

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 few examples of microwave emitters like cavity magnetron, the klystron, the travelling-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.

Radio waves v/s Microwaves

Features to differentiate

Radio waves

Microwaves

Frequency value

30KHz-300GHz

300MHz-300GHz

Penetration depth

Comparatively, long-wavelength result in deep penetration in objects with high density

Short wavelength results in less penetration on objects limited to small dimensions

Uniform heating

Radio wave heats the object uniformly

The microwave heats the product non-uniformly in an uncontrolled manner


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, more rain has passed through the microwave radiation

FAQ (Frequently Asked Questions)

1. Briefly explain the applications of microwave

A1. Microwave is commonly used in the oven for cooking food. At the same time, microwaves play a crucial role in communication technology as explained below.

Microwaves are used in cell phones. Microwave is the carrier of the signals of cell phones. With the help of frequency modulation, the caller's sound waves are encoded in microwaves by changing its frequency. These encoded microwaves are transmitted to cell tower via air. Then wave traverse to switching centre from cell tower, and finally, it reaches another cell tower of the receiver. At the receiver end, again, the microwave is decoded to sound wave. The microwave is interrupted by the building. That's why cell towers are on the outskirts and well above the ground to prevent obstruction.

Microwave is used in Radio Detection and Ranging (RADAR) technology. This technology is utilized in radar guns to find over speeding vehicles. Radar guns send a small microwave. Microwave is reflected by the metallic surface of the vehicle and thus detected by the receiver of the radar gun. This feature is also utilized in tracking storms, managing air traffic.


2. How is the food heated or cooked inside a microwave oven?

Water molecules strongly absorb the microwave energy of specific frequency. The absorption of the microwave by water causes water molecules to vibrate, which results in the increment of the kinetic energy of the water molecules.  Due to which the temperature of the materials containing water molecules increases. If we use frequency in the microwave, which is completely absorbed, the chances are that the food will only be cooked outside. As most of the energy is absorbed by the outer surface of food, not enough energy penetrates it. Thus, the setting of the microwave oven is such that it emits the microwave of frequency, which also penetrates the food. Once the microwave radiation penetrates the food, heat is spread all over the food by the mechanism of conduction and convection.

We should be cautious while using the microwave oven because our human body contains water molecules in our cells. Microwave oven radiation at high intensity could be dangerous as it can burn the body tissue by heating the cells. The radiation is limited inside the oven by placing the reflecting metal case and metal grid in the door.