Electromagnetic radiation: consists of energy propagated by electric and magnetic fields that increase and decrease in intensity as they move through space. (ex. visible light, x-rays, and microwaves) In a vacuum, electromagnetic radiation moves at 3 x 108 m/s (the speed of light, c: c = v x . The amplitude is related to the intensity of radiation, or its brightness in the case of visible light. All waves in the spectrum travel at the same speed through a vacuum but differ in frequency and, therefore, wavelength. The spectrum is a continuum of radiant energy so each region meets the next. Light of a single wavelength is called monochromatic. Ranges from very long radio waves to very short gamma rays and includes the visible region b/w wavelengths. The distinction between energy and matter: refraction and dispersion: light of a given wavelength travels at different speeds through various transparent media.