[Physics Class Notes] on Microwaves Pdf for Exam

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

1. Microwaves are produced by special vacuum tubes like the klystron, magnetron, and Gunn diode.

2. 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 th
e 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.