What is the use of frequency ?and why is it considered the one that carries information ?
This article is based on an experiment that shows the relationship between the frequency and waves to answer the question: Why is the frequency considered as the one that carries information?
I will be explaining the experiment objectively step by step to reach the conclusion and give an opinion based on facts.
Let’s start by defining Radio waves.
Radio waves
Radio waves are a type of Electromagnetic radiation (EM) which has longer wavelengths than the infrared light in the electromagnetic spectrum. All waves have a wavelength, amplitude and a frequency.
They have wavelengths from 1 millimeter to 100 kilometers and corresponding frequencies from 300 GHZ to the lowest: 3khz.
Radio waves are used for fixed and mobile radio communication, broadcasting, radar and other systems; it is used by multiple devices such as cellular telephones and televisions, these devices receive radio waves and convert them to mechanical vibrations in the speaker to create sound waves.
To learn more about this, check this.
We can extract two important information pieces from what we said:
First:
Waves are used to communicate thus they carry information; we can also say that information is sent in form of waves.
Second:
Each wave has a frequency therefore there must be a relationship between the wavelength and the frequency.
PS: The wavelength is the distance between two peaks (high points).
So, what is frequency?
Frequency is simply defined as the number of waves that passes a fixed point in a précised amount of time; in other words, it’s the number of completed cycles per second. The frequency’s unit is the hertz abbreviated Hz
For example, 50 cycles per second equals 50Hz or if one cycle’s time is 0.5 seconds then the frequency would be 2 per second or 2 Hz.
Experiment
As information is carried by waves, we took an example of the sound wave to explain the relationship between the frequency and the wave.
We will take a speaker and let it make one short burst to create a pulse wave. After that we will try to find the speed of sound.
By the speed of sound we mean the speed of the disturbance as it moves through the air’s molecules.
The speed wave that was made by the speaker is called a longitudinal wave because it travels in parallel to the line traced out by the oscillation of the medium (speaker), (view in Figure 1).
We will take a look at the graph of the air displacement versus the position of the air. We see that the direction in which the wave is going is from left to the right, when the latter travels, its shape travels to the right ( view in Figure 2).
This allows us to find the speed of the wave by finding the speed of any point on the wave shape.
To find a formula of the velocity (speed) of the wave , we watch closely one of the air molecules, it takes a period (T) for this molecule to move back and forth through a full cycle ; during this time the wave shape has moved forward one complete wavelength (view in Figure 3).
The reason for this to happen is simple: the molecule has to be back to its initial place where it started after one period; consequently, the wave has to overlap with its initial shape after one period T. (view in Figure 4).
Let’ go back to the speed now. Since the speed is defined to be the distance per time (Speed=Distance/Time), the speed of a sound wave has to be the wavelength of the wave divided by the period of the wave (V=Speed=λ/T).
We know that the wave is traveling forward one wavelength per period (view in figure 5) and we also know that the frequency is defined to be 1 over the period (f=1/T) we can now rewrite the formula as speed equals wavelength times frequency (speed=λ/T).
This formula is accurate for all kinds of waves not just sound waves because a wave has to move one wavelength for every period.
Note :
Increasing the frequency will not increase the speed because it will make the wavelength decrease, by that factor, the speed of the wavelength will remain the same and to change the speed of sound we should change the medium or the properties of the medium that the sound wave is traveling in for example : ( to change the speed of sound in the air we can change its temperature or humidity or density or replace the air completely by another material like : water or metal or helium ) .
Also if we change the amplitude, the speed of the sound wave will not change, if we create a sound pulse with a larger amplitude it won’t travel any faster than a sound pulse with a small amplitude in the same medium, it will just be louder, in other words yelling won’t make others hear you faster they will just hear a louder sound when the sound wave arrives at their location) , (view in Figure 6).
Conclusion
The information in space is carried in form of a wave which is called the carrier wave that’s why we search for the frequency to get information about the wave and since most waves goes at the speed of the light, it is hard to find the difference between them unless we have the frequency and the wavelength, i think that this resumes the use of frequency and why it is needed to reach the information that we seek .
I will add that the wavelength and frequency of light are closely related. The higher the frequency, the shorter the wavelength.
Because all light waves move through a vacuum at the same speed, the number of wave crests passing by a given point in one second depends on the wavelength. That number, also known as the frequency, will be larger for a short-wavelength wave than for a long-wavelength wave.
The equation that relates wavelength and frequency for electromagnetic waves as described above is: λf=c where λ is the wavelength, f is the frequency and c is the speed of light. So the relation between the frequency and wavelength is proportional.
