Jasles Rlaas, age l2, of Ottawa, Ont., Canada, for his question:
What is the spectrum?
In the world of ancient Rome, the word specere meant to look but through the ages, this old Latin word has taken an eerie turn. We borrowed it to make our word specter or spectre, meaning a spooky ghost. We also adopted it to create the scientific word spectrum and its plural form spectra.
A spectre, of course, is an impossible spook. Whether you see it or not depends upon your mental balance and the state of your imagination. The related word spectrum, however, is a scientific reality but it also has some spooky features. It may or may not be seen, heard or felt but the spectrum of science is factual and not imaginary.
The spectrum of science reveals an orderly pattern of energy which takes many forms. The radiant energy of the sun enfolds light and heat, radio and X rays. These and other forma of solar energy speed through space at about l86,000 miles a second. The different forms of energy travel together in pulses called wave lengths.
A wave length of energy compared to a wave of the sea has a crest and a trough and travels a set distanee from crest to crest in a set period of time. The sun's energy enfolds countless different wave lengths. The wave lengths of visible White light bring us sunshine. The wave lengths of infrared bring us heat. There are other wave lengths of radio, magnetic and electric energy.
All these and other wave lengths are grouped together as electromagnetic energy. Most wave lengths are unbelievably small and the distance from crest to crest is measured in millimicrons or Angstroms. The frequency of a wave length is its pulses per second, and some have frequency numbers higher than 30 followed by l0 zeroes. Nevertheless, the wave lengths of electromagnetic energy can be arranged in orderly sequences.
This tricky task was worked out long ago in the electromagnetic spectrum. Various wave lengths are arranged in order from the longest to the shortest. The different forms of energy have their own bands in the big electromagnetic spectrum. The radio spectrum can be heard.9 the infrared spectrum can be felt as heat and the most dramatic band is the spectrum of visible light. When sunlight strikes a prism, its various wave lengths are bent at different angles. They fan out separately and our eyes see them as the orderly colors of the rainbow.
The various spectra of energy are full of scientific information. spectroscopy, the study of spectra, is one of the most useful and reliable fields of science. One of its most dependable instruments is the spectroscope used to analyze light spectra from near and far. It can tell the temperature of a star hundreds of light years away. It can reveaI what gases it contains and even whether the distance between us and the star is increasing or decreasing.