Electromagnetic Waves and Spectrum

Study Notes

Electromagnetic Waves

Electromagnetic (EM) waves are transverse waves composed of oscillating electric and magnetic fields.
EM waves travel at the speed of light (3.0 x 10^8 m/s) in a vacuum.
EM waves can travel without a medium.
The electric and magnetic fields in an EM wave are perpendicular to each other.

The Electromagnetic Spectrum

The electromagnetic spectrum classifies different types of EM waves according to their frequency, wavelength, and energy.
Each type of EM wave has unique characteristics and applications.

Radio Waves

Radio waves have the longest wavelengths and lowest frequencies in the electromagnetic spectrum.
Radio waves have wavelengths ranging from 1 cm to 1 km and frequencies from 30 GHz to 300 kHz.
Different bands of radio waves exist:
- Extremely Low Frequency (ELF): Frequencies less than 3 kHz, wavelengths greater than 100 km, naturally generated in the atmosphere.
- Very Low Frequency (VLF): Frequencies from 3 to 30 kHz, wavelengths from 10 to 100 km, used for military communications with submarines.
- Low Frequency (LF): Frequencies from 30 to 300 kHz, wavelengths from 1 to 10 km, used for long-distance communication.
- Medium Frequency (MF): Frequencies from 300 kHz to 3 MHz, wavelengths from 100 m to 1 km, used for AM broadcasting and air traffic control.
- High Frequency (HF): Frequencies from 3 to 30 MHz, wavelengths from 10 to 100 m, used in international broadcasting.
- Very High Frequency (VHF): Frequencies from 30 to 300 MHz, wavelengths from 1 to 10 m, used in digital audio broadcasting and mobile radios.
- Ultra High Frequency (UHF): Frequencies from 300 MHz to 3 GHz, wavelengths from 10 cm to 1 m, used in television broadcasting.

Microwaves

Microwaves have frequencies higher than radio waves, ranging from 300 MHz to 300 GHz.
Microwaves are used in various applications, including:
- Global Positioning System (GPS) (L-bands)
- Active Remote Sensing
- Radio Detection and Ranging (RADAR)

Infrared (IR) Waves

Infrared waves reside between microwaves and visible light, with frequencies from 3 x 10^11 to 4 x 10^14 Hz.
They are grouped into near, mid-, and far infrared regions.
Infrared radiation is invisible to the human eye but can be detected as heat.
Applications include:
- Remote sensing
- TV remote controls
- Thermal imaging

Visible Light

The only part of the electromagnetic spectrum visible to the human eye.
Frequencies range from 400 to 700 nm.
Different colors of light are caused by differences in their wavelengths, creating the rainbow: red, orange, yellow, green, blue, indigo, and violet.
Applications include:
- Spectral imaging

Ultraviolet (UV) Waves

UV radiation extends from the violet end of the visible light spectrum through X-rays, with wavelengths from 10 to 400 nm.
Most UV radiation received from the sun is classified as UVA, UVB, and UVC.
- UVA is the least harmful.
- UVC is the most harmful but absorbed by the ozone layer.
- UVB can cause sunburn and cellular damage due to chemical reactions on the skin.
- UVB can lead to the production of free radicals and DNA damage.

Description

This quiz covers the fundamentals of electromagnetic waves and the electromagnetic spectrum. It includes information on the characteristics of different types of EM waves, such as radio waves, and their classifications based on frequency and wavelength.