What are Waves?

What is a wave, actually? If you ask the most popular encyclopedia of our time, Wikipedia, a wave is „a disturbance or oscillation (of a physical quantity) that travels through matter or space, accompanied by a transfer of energy”. Sounds complicated? It doesn’t have to be – let’s look at the topic together and we’ll see that waves are easy to understand. They are around us all the time.

When the sun paints our world gold in the early morning hours, when beautiful music reaches our ears or when a single drop disturbs the surface of a liquid at rest – these phenomena are all related to waves. Before we take a closer look at waves and how they are involved in the phenomena described above, we first need to understand what constitutes a wave. So, back to the first question: What are waves?

The structure of a wave

We have all seen waves – whether in nature or in a physics textbook at school. Its basic structure is always the same: It has a peak and a trough, and a certain distance from peak to peak or from trough to trough. A wave’s oscillation is determined by means of its amplitude. It expresses how high the wave’s peak is (or how deep its trough) in relation to its baseline; the amplitude is a measure of the wave’s maximal displacement. The distance from one peak or trough to the next is called wavelength. It is denoted with the Greek letter lambda (λ). The greater the wavelength, the lower the wave’s peak. So, what are waves? Peaks and troughs with a specific height or depth and a certain distance from each other that travel through space.

The amplitude is a measure of the wave's maximum displacement. The distance from one peak or trough to the next is called wavelength.

The frequency makes the sound

There is a third important property for characterizing a wave: its frequency. It is the reason why light is blue, yellow or red, or why a base sounds different than a flute. The frequency is the number of a wave’s occurrence per second; its unit is hertz (Hz).

Every day, what we hear are waves. The relation of sound and frequency is easily explained by the example of a guitar string: The higher a wave’s frequency – its oscillations per second –, the higher the sound it produces. The closer your hand on the guitar’s neck travels towards the hand hitting the strings, the more the wavelength is shortened. But how does that change the pitch of the sound? Wavelength and frequency, in other words how often the string oscillates per given time, are related: The shorter the wavelength the higher the frequency and thus the pitch of the sound: The shortened string can vibrate more often in the same time period.

The same goes for a plastic ruler placed on the edge of a desk and made to oscillate. The more of the ruler is placed beyond the edge, the longer the wavelength and the lower its frequency will be and the less oscillation it will produce in a given time. When you reduce the length of the ruler that runs beyond the edge, the wavelength of its oscillation will decrease and the frequency will increase – and you will hear a higher pitch. In countless everyday experiences like this, what we encounter are waves.

Wavelength and frequency are related by the wave’s propagation velocity. And the propagation velocity in turn depends on the medium through which the wave is travelling. This is why waves can tell us something about the material through which they are travelling. Many analytical methods make use of the interaction of waves and matter.

Waves at Anton Paar

Yes, waves are exciting. We know, because we work with them every day. Anton Paar develops and produces high-tech measuring instruments that can create and measure waves and oscillations – like density meters and optical refractive index- or CO2 analyzers. Also our microwave synthesis devices and polarimeters make use of waves. Waves are part of our work; they are our “daily bread”.

Are you looking for further information or do you have any further questions? We look forward to helping you out – contact us via www.anton-paar.com.

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