II.

Properties

There are three phenomena through which energy can be transmitted: electromagnetic radiation, conduction, and convection (see Heat Transfer). Unlike conduction and convection, electromagnetic waves need no material medium for transmission. Thus, light and radio waves can travel through interplanetary and interstellar space from the sun and stars to the earth. Regardless of the frequency, wavelength, or method of propagation, electromagnetic waves travel at a speed of 3 × 10¹⁰ cm (186,272 mi) per second in a vacuum. All the components of the electromagnetic spectrum, regardless of frequency, also have in common the typical properties of wave motion, including diffraction and interference. The wavelengths range from millionths of a centimeter to many kilometers. The wavelength and frequency of electromagnetic waves are important in determining heating effect, visibility, penetration, and other characteristics of the electromagnetic radiation.