Figure 2.25

The electromagnetic spectrum. Electromagnetic radiation travels in waves. Shorter wavelengths, shown on the left, include cosmic rays, gamma rays, X-rays, and ultraviolet rays. (Cosmic rays originate in distant exploded stars in space rather than the Sun.) Only visible wavelengths can be seen with our eyes. In the visible portion of the spectrum (shown in the inset), violet has the shortest wavelengths, at 0.4 μm, and red has the longest wavelengths, at 0.7 μm. Longer-than-visible wavelengths, shown on the right, include infrared radiation, microwaves, and TV and radio waves.