# Electromagnetic Waves

#### Topics

• Sources of electromagnetic waves: Hertz's experiment
• Nature of electromagnetic waves
• Speed of electromagnetic waves
• Production and properties of electromagnetic waves
• Electromagnetic Waves and Their Characteristics
1) Energy density
2) Poynting vector
3) Momentum

## Notes

### INTRODUCTION

An electromagnetic wave is a transverse wave that results from a changing magnetic field and an accompanying changing electric field. The time-varying magnetic and electric fields are perpendicular to one another and to the direction of transmission.

Thus, the electric and magnetic fields that make up electromagnetic waves act at right angles to one another and to the direction of transmission, while also fluctuating sinusoidally over time.

## Notes

HISTORY OF ELECTROMAGNETIC WAVES

• Maxwell made a theoretical prediction about electromagnetic waves in the year 1865. He claimed that an accelerating charge creates a magnetic field around it.
• Hertz experimentally generated and spotted electromagnetic waves in 1887 with a wavelength of roughly 6 m.
• J.C. Bose succeeded in creating electromagnetic waves with a wavelength ranging from 5 to 25 mm seven years later.
• In 1896, Marconi discovered that electromagnetic waves could travel up to several kilometres if one of the spark gap terminals was connected to an antenna while the other terminal was grounded.
• The earth cables and antenna from a capacitor's two plates emit radio frequency waves.
• An antenna earth system could be used as a detector to pick up these waves at a great distance.
• With the use of these setups, Marconi became the first person to establish wireless communication over the English Channel, or a distance of around 50 kilometres, in 1899.
If you would like to contribute notes or other learning material, please submit them using the button below.

#### Video Tutorials

We have provided more than 1 series of video tutorials for some topics to help you get a better understanding of the topic.

Series 1

Series 2

### Shaalaa.com

Electromagnetic Waves part 1 (Introduction) [00:13:12]
S