Microwave: Electromagnetic Spectrum

Our ancestors would sit around smoky wood fires for hours boiling food, but now all we have to do is press a few buttons and toss food inside a microwave oven, and our meal is ready in a minute or two. Microwave ovens are quick and efficient because they channel the heat directly to the molecules inside the food. In this article, let us learn about microwaves and their various properties and applications.

Table of Contents

What are Microwaves?

Microwaves are defined as electromagnetic radiations with a frequency ranging between 300 MHz to 300 GHz. In contrast, the wavelength ranges from 1 mm to around 30 cm. Microwave radiation is commonly referred to as microwaves. They fall between infrared radiation and radio waves in the electromagnetic spectrum. A few of the properties of microwaves are as follows:

  • Metal surfaces reflect microwaves. Microwaves with a certain wavelength pass through the earth’s atmosphere and can be useful in transmitting information to and from satellites in orbit. Hence, the satellite dishes are made of metal as they reflect microwaves well.
  • Microwaves of certain frequencies are absorbed by water. This property of microwaves is useful n cooking. Water in the food absorbs microwaves, which causes the water to heat up, therefore cooking the food.
  • Microwave transmission is affected by wave effects such as refraction, reflection, interference, and diffraction.
  • Microwaves can pass through glass and plastic. This is the reason why we use a plastic or glass container in a microwave oven and not metal containers, as metal reflects microwaves.

Applications of microwaves

The uses of the microwave are similar to that of radio waves. They are used in communications, radio astronomy, remote sensing, radar, and of course, owing to their heating application, they are used in cooking as well. Why do mobile phones use microwaves? Because microwaves can even be generated with the help of small antennas, so mobile phones need not be of large size.

Microwaves and Cellphones

Cell phone signals are carried through the air as microwaves. The caller’s sound is encoded in microwaves by changing the frequency of the waves. This is called frequency modulation. The encoded microwaves are sent to the cell tower through the air. From the cell tower, the waves travel to a switching centre. From there, they go to another cell tower and from the tower to the receiver of the person being called. The receiver changes the encoded microwaves back to sound. Microwaves can be interrupted by buildings and other obstructions, so cell towers must be placed high above the ground to prevent the interruption of cell phone signals.

Microwaves and Radar

RADAR stands for Radio Detection and Ranging. Police use radar guns to detect over-speeding vehicles.  A radar gun sends a short burst of microwaves. Microwaves reflect from the oncoming vehicle and are detected by the receiver in the radar gun. The speed of the vehicle is computed from the speed of the vehicle. Radar is used for tracking storms, detecting air traffic, and other purposes.

Microwave - Electromagnetic Spectrum

Interesting Fact About Microwaves

Something which is not very well known is the use of microwaves in getting the first clues to the occurrence of the Big Bang. In the 1960s, two scientists, who happened to be working with special low-noise antennae, noticed something extraordinary. They were picking up noise from all directions, and they noticed something stranger. The noise from all directions did not vary in its intensity. Arno Penzias and Robert Wilson, the two scientists, figured that if it came from anywhere on earth, then the direction would be pretty specific… but it wasn’t! They realized that they had discovered cosmic microwave background radiation by mistake! This microwave radiation fills the entire radiation and was our first clue to the occurrence of the Big Bang!

There is a wide belief that microwaves emit radiation they are not suitable for health. But microwaves fall under the low frequencies of the electromagnetic spectrum. They also have low energies. Therefore, they do not have enough energy to chemically change substances through ionization. Radiation here means having energy and not radioactivity. And some studies have carcinogenic effects (these are not the same as previously mentioned high energy emitting exposure).

Frequently Asked Questions – FAQs


What is electromagnetism?

Electromagnetism is a branch of physics that deals with the study of electromagnetic forces. Interaction between electrically charged particles and associated fields is known as electromagnetic forces.

State true or false: Electromagnetic forces are one of the fundamental forces.


How electromagnetic radiation occurs?

Electromagnetic radiation occurs when an atomic particle, like an electron, is accelerated by an electric field, causing it to accelerate.

Can microwaves pass through glass?

Yes, microwaves can pass through glass.

How are microwaves produced?

Microwaves are produced by special vacuum tubes referred to as klystrons, magnetrons, and Gunn diodes.

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