How are electromagnetic waves classified based on their wavelengths?

Electromagnetic waves are classified into different types based on their wavelengths (or equivalently, their frequencies). This classification forms the electromagnetic spectrum, which includes the following major categories (from longest to shortest wavelength):

1. Radio Waves
   • Wavelength: > 1 millimeter
   • Used in radio, television, and wireless communication.
2. Microwaves
   • Wavelength: 1 millimeter to 1 centimeter
   • Used in radar, satellite communication, and microwave ovens.
3. Infrared (IR)
   • Wavelength: 700 nanometers to 1 millimeter
   • Emitted by warm objects; used in remote controls and thermal imaging.
4. Visible Light
   • Wavelength: 400 to 700 nanometers
   • The only part of the spectrum visible to the human eye (ROYGBIV).
5. Ultraviolet (UV)
   • Wavelength: 10 to 400 nanometers
   • Comes from the sun; causes sunburn and is used for sterilization.
6. X-Rays
   • Wavelength: 0.01 to 10 nanometers
   • Penetrate soft tissue; used in medical imaging.
7. Gamma Rays
   • Wavelength: < 0.01 nanometers
   • Emitted from radioactive materials and nuclear reactions; used in cancer treatment.

Key point: As wavelength decreases, frequency and energy increase. Thus, gamma rays are the most energetic, and radio waves are the least energetic.