What is a Wavelength?
A wavelength is the distance in between the repeating units of a wave, as measured from one point on a wave to the corresponding point in the next unit. For example, the distance from the top — called the crest — of one wave unit to the crest of the next is one wavelength. In physics notation, wavelength is often designated by the Greek letter lambda. Wavelength is inversely proportional to the frequency of a wave. In other words, the shorter the wavelength is, the more wave units will pass in a given amount of time. A wave is simply energy that moves through a medium. Outside of the context of physics, ocean waves are an excellent example of how waves work. Except where the wave breaks, it is not so much the water that moves as it is energy in the water, which produces an up-and-down motion that is noticeable a short distance from the shore. Physicists study light and sound waves, as well as waves of other types of energy, and in this context, wavelength is an important factor to de
If we think of light as a form of waves (which is only an approximation to our current model), than a wavelength is the distance from the crest of one wave to the crest of another. For instance, blue light has a much shorter wavelength than red light. If you were to have electromagnetic radiation with a longer wavelength than red, we call it infrared. Longer than that, and we call it microwaves. If the radiation being considered has a still longer frequency, than they are radio waves (which also contain TV and radar waves). On the other side of the spectrum, electromagnetic (em) radiation with a shorter wavelength than blue (less distance between each crest) is called ultraviolet. Still shorter are what we call X-rays, and shorter still are called gamma rays. Telescopes can be built to look at many different frequencies. Of course, the telescopes we are most familiar with look at visible light. However, our atmosphere filters out most infrared, all microwave, most ultraviolet (filtered
Wavelength is the distance between two adjacent crests in a wave front (or, correspondingly, two adjacent troughs). Easiest way to see this by tossing a rock into a still pond. The physical distance between the high points of two waves next to each other is the wavelength. A similar concept is the frequency. The frequency is the number crests that will pass through a plane in a given length of time, like a second. Toss that same rock and you might notice a leaf bob up and down. It doesn’t go anywhere, it just moves up and down as the waves pass through. The frequency is the number of times the leaf goes up and down in one second. Mathematically, the wavelength is 1/frequency. Both are extremely useful. The frequency (or wavelength) in sound determines pitch, which gives us sound, music, etc. Since light and all electromagnetic energy is a wave (mostly), different colors are nothing more than EM energy at different wavelengths within the visible spectrum.
