• ### Browse All Lessons

##### Assign Lesson

Help Teaching subscribers can assign lessons to their students to review online!

 Tweet

# The Electromagnetic Spectrum

This lesson aligns with NGSS PS4.B

Introduction
Have you ever stepped outside after a rain shower and observed a magical rainbow that stretches from the shortest colors like violet and blue to the longest colors like red? The light bulbs emit visible light, which allows you to see everything around you. When you watch your favorite cartoons on TV or enjoy a phone call from your buddy, what connects these diverse experiences? They all share a common element, the electromagnetic spectrum, which is a range of all types of electromagnetic radiation. In this article, we will explore the concept of electromagnetic spectrum and the characteristics of electromagnetic waves.

The Electromagnetic Spectrum
The electromagnetic spectrum is a continuum of electromagnetic radiations with varying wavelengths and frequencies. It includes all types of electromagnetic radiation, from the shortest gamma rays to the longest radio waves. Electromagnetic waves consist of both electric and magnetic fields that vibrate perpendicular to each other as they travel. These waves carry energy and can move through a vacuum.

The Role of Wavelength
To understand the electromagnetic spectrum, you have to understand the wavelength. Because the electromagnetic spectrum arranges all the different electromagnetic waves according to their wavelength.

Imagine you’re at the beach, watching the water move in and out. When you look from the top of one wave to the top of the next one, that is what we call a wavelength.

If the wavelength is long, you will notice fewer waves in a given time. while if the wavelength is short, you will experience more waves passing by at the same time.

Characteristics of Electromagnetic Spectrum
The arrangement of electromagnetic waves from the longest wavelength to the shortest wavelength or from low to high frequency goes as follows: Radio waves, Microwaves, Infrared waves, Visible light, Ultraviolet light, X-rays, and Gamma rays.

Radio waves cover a wide range of waves within the electromagnetic spectrum. Among all electromagnetic waves, they possess some of the longest wavelengths and shortest frequencies. The reason is that radio waves are low-energy waves. Despite being low in energy, radio waves carry enough energy to be effectively used for broadcasting radio signals.

Radio stations transmit sound information through radio waves by modifying either the wave’s amplitude or its frequency. This process of altering amplitude or frequency is known as modulation.

• A radio station transforms sound into an electric current. This electric current generates radio waves that are transmitted in all directions through the antenna.
• A radio receives radio waves and transforms them into an electric current. This electric current is then converted back into sound, allowing us to hear transmitted sound.
We know that there are AM radio stations and FM radio stations. It is important to note that AM stands for amplitude modulation, while FM stands for frequency modulation. Comparatively, AM radio waves possess longer wavelengths than FM radio waves.

AM radio waves can reflect off the ionosphere which helps AM waves travel long distances. On the other hand, FM radio waves can pass through the ionosphere. Therefore, FM waves cannot travel as far as AM waves.

Although AM radio waves can travel faster than FM waves. But many stations prefer to use FM waves.  This preference is because frequency modulation can code more information compared to amplitude modulation. Consequently, music broadcasts from FM stations sound better.