THE undulatory is the branch of Physics which studies all the phenomena related to the different types of waves existing in nature. We are daily surrounded by technologies whose working principle is the waves. Mobile phones, wireless Internet, ultrasound diagnosis, satellites meteorological and radio communication are some examples of Undulating applications.
Check out a list of five things you need to know about waves now:
I. There is a minimum distance for the echo to occur
The so-called sound persistence is the minimum time interval necessary for the human ear distinguish between two sounds. If two different noises reach the human hearing aid in a time less than 0.1s they will not be interpreted as two, but only as a single sound. By understanding this, we can distinguish between echo and reverberation:
Echo: Occurs echo when the sound produced by a source is reflected by an obstacle and the reflected sound reaches the emitter in a time equal to or greater than 0.1 s.
Reverberation: Occurs
reverberation when the sound produced by a source is reflected by an obstacle and the reflected sound reaches the emitter in less than 0.1 s.
Being 0.1 s the minimum time for the echo to occur and 340 m/s at speed of sound in the air, we can determine the minimum distance the emitter must be from the obstacle for an echo to occur.
Knowing that the velocity is defined as the ratio between the distance covered by a mobile (d) and the time spent (t), we can write:
v = d ÷ t
As for the occurrence of the echo the sound must leave and return to the emitter, the distance must be doubled:
v = 2.d ÷ t
v. t = 2.d
340. 0.1 = 2.d
34 = 2.d
d = 17 m
We conclude that, for the occurrence of the echo, the obstacle that will reflect the sound must be at least 17 m from the emitting source.
II. Frequency does not change when refraction occurs.
Occurs refraction when a wave changes its propagation medium. This phenomenon is characterized by a change in wave velocity, which will present different values for different propagation media. A very important aspect of refraction is that the waves that change their propagation medium do not have their frequency changed, as the frequency of a wave depends on the source and will only be changed if the source itself increases or decreases its oscillation.
III. Sound is faster on solids
O sound it is a mechanical wave and as such it needs a means of propagation. There will be no sound if there are no molecules of a propagation medium, so we always hear that sound it does not propagate in a vacuum, because in a vacuum there is a total lack of molecules, preventing the propagation of waves mechanics.
The closer the molecules that make up a medium are, the better the propagation of sound waves. Therefore, we can conclude that sound will propagate faster in solids due to the proximity of the molecules.
VSOUND(S) > VSOUND (L) > VSOUND (G)
The table below indicates the sound propagation velocity values for different media.
IV. Speed is a characteristic of the propagation medium.
Imagine that the waves generated in a string propagate with any velocity V when the source maintains a certain frequency. If the source increases or decreases the frequency of vibration, the wavelengths will be such that the value of the propagation velocity of the waves in the string will always be maintained. The speed of the waves is a propagation medium characteristic and will not change even with the change of frequency generated by the source.
V. Blue is the hottest color!
Common sense tells us that the color blue is always related to the cold and the red color is always related to the heat, but the electromagnetic spectrum shows us just the opposite! The higher the frequency associated with a wave, the greater its energy. The closer to the blue and violet colors, the higher the radiation frequencies, therefore, the greater the energy released. THE radiation emitted by a black body at 1000 K (1273 °C) it is reddish. The radiation emitted by the same body at 4000 K (4273 °C) is predominantly blue.
By Joab Silas
Graduated in Physics
Source: Brazil School - https://brasilescola.uol.com.br/fisica/5-coisas-que-voce-precisa-saber-sobre-ondas.htm
