Wave Length
the distance, in all of successive waves. tion of light these distances are almost In the wave moinconceivably minute. The wave in the from about 33000 inches in the red end visible part of the spectrum ranges to about 68000 inches in the violet. In it is brightest (in sunlight) the wave is the yellow part of the spectrum, where about 30 inches. When we remember that light travels through space with a velocity of about 186,000 miles per sec- , if we wish to get some faint idea of the almost inconceivable frequency of the vibrations, multiply the denominators of the above fractions by the number of inches in 186,000 miles. We shall find that the extreme red light vibrates about 400,000,000,000,000 times, the yellow light about 510,000,000,000,000 times and the extreme violet light about 800,- 000,000,000,000 times per second. The WAVRE difference of color is simply a difference of wave length and frequency, for, so far as known, they all travel with the same velocity. There are heat rays, or vibrations, which are invisible to the eye, of much greater wave length and less frequency. These are below the visible red in the spectrum. There is no difference between the radiations that we call by the different names of heat, light, and chemical (or actinic) rays except in the wave lengths and frequency of their vibrations.
WAVRE (vävr), town in the Belgian province of Brabant, 15 miles S.
E. of Brussels; pop. about 10,000. Here on June 18, 1815, there was a fiercely contested battle between the Prussians under Thielmann and the French under Grouchy, in which the Prussians successfully prevented the French from joining Napoleon at Waterloo. See WATERLOO, BATTLE OF.