Ricci Colmer, age 15, of Winnipeg, `Manitoba, Canada, for his question:

How are wavelength, frequency and velocity related?

These terms are used to define invisible energies that travel from here to there in pulsing waves. Velocity is the speed at which they travel. Wavelengths measure the size of the pulses. Frequency counts the number of times they pulse per second. Solar radiation is a package of assorted energies including light and radio. They all travel at the same velocity. But they pulse along in waves of different lengths, vibrating at different frequencies.

Sound travels in waves of energy that vibrate at so many frequencies per second. High notes have hi?h frequencies that vibrate faster and low notes vibrate at lower frequencies. Sound energy has to pulse along through a surrounding medium, which may be molecules of gases, liquids or solids. Its velocity through ordinary air is about 1,110 feet per second. Dense, elastic mediums help it to go faster and through steel its velocity per second is 16,400 feet.

A whole range of other energies are far more dramatic than sound, though the terms wavelength, frequency and velocity still apply. This group includes the package of radiant energies poured forth by the sun. They travel in waves of assorted lengths, pulsing at different frequencies. They need no medium through which to travel and all of them whip across space at the same velocity, approximately 186,000 miles per second.

These cosmic speeders are called electromagnetic energies, because their pulsing Haves are surrounded by equally balanced fields of electricity and magnetism. They include visible light, infrared and ultraviolet light, radio and microwaves, gamma rays and X rays. All travel at the same velocity in pulses of energy, somewhat like waves of the sea. These wavelengths are measured by the distance between one crest and the next.

The different kinds of electromagnetic energy travel in different wavelengths, some longer and some shorter. The longest radio wavelengths measure many miles. The shortest ga~ama ray wavelengths measure about one billionth of an inch.

A11 these invisible wavelengths vibrate so many times per second    which gives their energy frequency. Longer wavelengths have lowyer frequencies, shorter wavelengths have higher frequencies. The various forms of this energy are arranged in a row, according to wavelengths and frequencies. This chart is the electromagnetic spectrum.

Short wavelengths with high frequencies are on the left, longer wavelengths with lower frequencies are graded toward the right side of the spectrum. Midway is a narrow section giving the bands tie see in the rainbow spectrum of visible light.

The velocity of all forms of electromagnetic energy equal the speed of light. Their different wavelengths can be compared to longer and shorter strides, passing a given point during one second. Shorter wavelengths must take more steps to keep up with the parade. 'fence, shorter wavelengths have higher frequencies and loner wavelengths have lower frequencies.