Electromagnetic waves are all around you— the radio you listen to, the TV you watch, the microwave oven you use for cooking, and the X-rays your doctor uses. All employ electromagnetic waves. But what are electromagnetic waves? Learn in detail about electromagnetic waves, their types and examples.

What is an Electromagnetic Wave?

Electromagnetic waves definition: The waves produced when an electric field comes in contact with the magnetic field are called electromagnetic or EM waves. They are a composition of oscillating magnetic and electric fields that can be studied using Maxwell’s equations. 

Electromagnetic waves can be radio waves, microwaves, television waves, and more. The differing types arise from the difference in wavelength and frequency. 

How are Electromagnetic Waves Formed?

• A charged particle gives rise to an electric field.
• This electric field applies a force on other charged particles. 
• Positive charges get accelerated toward the direction of the electric field. Contrastingly, negative charges get accelerated in the opposite direction. 
• The moving charged particle gives rise to a magnetic field. 
• This magnetic field exerts a force on other charged moving particles. 
• This force is perpendicular to the velocity direction; thus, it changes their velocity, not the speed.
• As a result, an accelerating charged particle gives rise to an electromagnetic field. 
• Therefore, you can say that electromagnetic waves are magnetic and electric fields travelling via free space with the speed of light c.
• When the charged particle oscillates around an equilibrium position, it is termed an accelerating charged particle.  
• So, if its frequency of oscillation is f, the electromagnetic wave it produces will also have a frequency (f). 
• The following equation can give the wavelength λ of the electromagnetic wave:
  • λ = c/f

Properties of Electromagnetic Waves

Following are some key postulates regarding electromagnetic waves:

• Electromagnetic waves are transverse in nature.
• An accelerating charge can produce them.
• They require no medium for propagation.
• The direction of variation of electric (E) and magnetic (B) fields are perpendicular to each other and also perpendicular to the direction of propagation (c). 
• The following formula gives the frequency of an electromagnetic wave:

v= 1/2π√LC

• The variation in electric and magnetic field components remains in the same phase. So, the phase difference is zero. 
• The magnitudes of E and B are related as follows:

C= E/B

• The energy of an EM wave is divided on average equally between E and B. 
• The following formula gives the speed of an electromagnetic wave in a vacuum:

C= 1/√µ0 εο

Are Electromagnetic Waves Mechanical or Non-Mechanical?

It is to keep in mind that electromagnetic waves are non-mechanical in nature, they are transverse waves that are independent of medium. Electromagnetic waves transfer energy from a source (transmitter) to a receiver through oscillating electric and magnetic fields. Common examples include radio waves, microwaves, infrared radiation, visible light, ultraviolet rays, X-rays, and gamma rays.

Derivation of the Speed of EM Waves Formula

The formula for the speed of an electromagnetic wave in a vacuum can be derived as follows:

Since 1/ 4πεο = 9 x 109  and µ0 = 4π × 10-7  

Writing µ0 = 4π × 10-7  as  o4=10-7

On dividing the two equations: 1/4πεο= 9 x 109  by μο/4π =10-7 

You get 1/μoεο = 9 × 1016

It can be written as 1oo = (3 × 108 )2

Since it is known that 3 × 108 = c

So, the equation can be written as follows:

1/μoεο = c2  

Example 1. What is the wavelength of an infrared light photon that has a frequency of 2 x 1014 Hz? Solution: Infrared light lies in the electromagnetic spectrum. So, its relation between the frequency, wavelength, and velocity can be studied using the following formula:  λ = c/f Since c = 3 x 108 m/s and the given frequency is 2 x 1014 Hz, the value of the wavelength can be calculated using the wavelength formula. λ = c/f λ =3 x 108/2 x 1014 λ = 1.5 x 10-6m

Are Electromagnetic Waves Transverse in Nature?

Yes, Electromagnetic waves are transverse in nature. This means their electric field and magnetic field oscillate perpendicular to the direction of wave propagation.

This property follows from Maxwell’s equations in free space, which show that the electric field (E) and magnetic field (B) have no components along the direction of propagation. As a result, the oscillations occur at right angles to the direction in which the wave travels.

Because of this perpendicular arrangement, electromagnetic waves transfer energy while the electric and magnetic fields continuously oscillate mutually perpendicular to each other and to the direction of energy flow.

Formation, Sources, and Propagation of Electromagnetic Waves

Wondering how are electromagnetic waves formed? They are formed by accelerating charged particles. They’re mostly creating oscillating, mutually regenerating electric (E) and magnetic (B) fields that propagate through space at the speed of light (c≈ 3 x 108 m/s).

Some of the sources include:

• Antennas
• LC circuits
• Sun
• Interstellar plasma Jets
• Radioactive decay

Since these waves are transverse in nature, it means that their propagation is done in 3 ways, as we discussed earlier, their propagation is done by:

• Ground Wave Propagation: It travels along the surface of the earth and follows the curvature of the earth.
• Sky Wave Propagation: It travels upwards into the atmosphere, where it is reflected by the ionosphere back to the earth, allowing the signal to cover long distances.
• Space Wave Propagation: It travels directly from the transmitter to the receiver through the atmosphere, and you can see the application in mainly TV and Radio signals.

Types of Electromagnetic Waves and Their Uses

There are many forms of electromagnetic waves, some are distinguished by wavelength, and others are differentiated by frequency and energy. Although most of them are traveling at the same speed in a vacuum, they differ in how they interact with matter and where they are used in everyday life. Let’s understand it in a bit more detail.

What is an Electromagnetic Spectrum?

The range of electromagnetic waves frequencies and their respective wavelengths and photon energies is called an electromagnetic spectrum. 

To understand the electromagnetic spectrum, one should know about wavelength and frequency. Wavelength is the distance between adjacent crests in the adjacent cycles of a waveform signal. While the top part is the crest, the bottom is a trough. The long waves have a low frequency and energy, while the shorter waves have a comparatively high frequency and energy.

Points to Remember

Frequency decreases

————————————————————————————→ 

Gamma → X-rays → Ultraviolet → Visible → Infrared →Micro →Radio

————————————————————————————→

Wavelength increases

• Gamma rays have the highest frequency.
• Radio waves have the highest wavelength. 
• The speed remains constant. 

Crest, Trough, and Wavelength

So, an electromagnetic spectrum comprises waves of different wavelengths, from very long radio waves to short gamma rays. The electromagnetic spectrum includes the following waves, as shown in the figure. In order of their increasing wavelength, the rays are as follows:

Gamma rays < X rays < UV rays < Visible Light < Infrared rays <  Microwaves < Radio waves

Electromagnetic Waves Examples and Their Uses

The electromagnetic spectrum includes several electromagnetic wave types. Here is in detail about each one of them. 

Radio Waves

The waves with the longest wavelengths among all the EM waves. They can be a foot long or even up to several miles in length. These waves find application in data transmission via radio, satellites, computers, and radar. 

Microwaves

Shorter than radio waves, these microwaves measure in centimetres. They are extensively used as they can penetrate smoke, clouds, and light rain. The universe has immense cosmic microwave background radiation that scientists connect with the Big Bang.

Infrared

In between microwaves and visible light regions, infrared waves are often classified into near and far categories. Near-infrared waves lie closer to visible light, and they find applications in TV remotes to switch from one channel to another. Far infrared waves are away from visible light in wavelength and give off heat. 

Visible light

The light spectrum that the human eye can see is called the visible light spectrum. It covers wavelengths from 390 to 700 nm.

Ultraviolet

UV rays are the next shortest wavelength rays largely emitted from the sun. The ozone layer protects the earth from the sun’s harmful ultraviolet rays. Often some insects like bumblebees can see ultraviolet light. Powerful telescopes use UV rays to see the stars.

X-rays

As discovered by Roentgen, X-rays have even shorter wavelengths than UV rays. They can penetrate soft tissue and provide a picture of bones. Multiple exposures to X-rays carry a risk of cancer, but this risk is quite small.

Gamma rays

They are the shortest waves in the spectrum with the highest energy. Gamma rays find applications in cancer treatments and detailed imaging for diagnostic purposes. 

The following table enumerates the uses of electromagnetic waves:

Wave	Wavelength	Uses
Gamma rays	10-14 to 10-10m	It provides information about the structure of atomic nuclei It has medical applications too.
X-rays	10-11to 3 ×10-8m	It reveals the structure of inner atomic electron shells and crystals.  Helps in medical diagnosis. Assists in industrial radiography
UV rays	10-8 to 4 × 10-7m	Helps in the detection of invisible writing, forged documents and fingerprints. It helps detect forged currency as real banknotes do not turn fluorescent under  UV light. Helps in preserving foodstuffs and detecting adulteration Used in water sterilisation
Visible rays	4 ×10-7to 8 ×10-7m	Reveals structure of molecules and arrangement of electrons in external shells of atoms. Allows you to see objects
Infrared rays	8×10-7 to 5 × 10-3m	In greenhouse effect, it is responsible for keeping plants warm It helps to look through haze, fog, and mist in wars. Helps cure crop diseases Treats muscular strains In astronomy
Microwaves	10-3 to 3 × 10-1m	In radar Long-distance wireless communication via satellites  In microwave ovens
Radio waves	10-1 to 10-4m	In radio and television communication systems  Marine and navigation use

Propagation of Electromagnetic Waves

The sequence of electromagnetic wave movement is as follows:

Generation → propagation → reflection → reception

The EM waves can be propagated from the transmitter to the receiver in the following ways:

• Ground waves: They can be propagated along the surface of the ground, and the process is called ground wave propagation.
• Skywaves: When the EM waves are propagated via sky, it is called sky wave propagation. In this type of propagation, the waves get reflected back to the earth from the ionosphere.
• Space waves: EM waves often propagate from the transmitter to the receiver antenna without any reflection or refraction; then, it is called space wave propagation.

Difference Between Mechanical Waves and Electromagnetic Waves

So, what is the difference between electromagnetic waves and mechanical waves?

Basis of Comparison	Mechanical Waves	Electromagnetic Waves
Medium Requirement	Require a material medium (solid, liquid, or gas) to travel.	Do not require any medium and can travel through a vacuum.
Nature of Vibration	Caused by the vibration of particles in the medium.	Caused by oscillating electric and magnetic fields.
Speed of Propagation	Speed depends on the properties of the medium.	Travel at the speed of light in a vacuum (about 3 × 10⁸ m/s).
Type of Waves	Can be transverse or longitudinal.	Always transverse in nature.
Examples	Sound waves, water waves, seismic waves.	Light waves, radio waves, X-rays, gamma rays.

Frequently Asked Questions

Conclusion 

Electromagnetic waves are an integral part of our everyday life. They have vast applications in different fields, ranging from medical, army, and navigation to our household appliances. They play a vital role in communication and have contributed immensely to making our lives easier.