frequency sound has characteristics peculiar for a number of other phenomena that propagate through the wave.This is true, for example, light or X-rays.The frequency of the sound - it is a certain physical quantity, which is characterized by constant repetitions.It is determined by the ratio of the number of waves to the time interval during which they occur.For example, the frequency of a sound determines its height, we hear.Or do not hear if fluctuations are outside our hearing capabilities - infrastructure or ultrasound.If we are talking about light emission, depending on the frequency and wavelength, we see a different color spectrum from red to blue.
frequency sound and the Doppler effect
An interesting phenomenon associated with the considered value is called the Doppler effect (named after the scientist and discoverer).It can be seen on the example of the light waves, but the speed of light is very high (about 300,000 kilometers per second), and it makes it difficult to observe him in everyday conditions.And the speed of propagation of sound waves is much lower.So, what is the Doppler effect?Imagine, if you are on the side of the main road and is close to you from a distance the car with working siren.When he is still far away, the roar of the sirens will sound hollow to you.This means that the low frequency sound.But as we approach it, more will grow.You can hear more and more high-pitched tone that reaches a maximum when the car will pass by you.When you pass an object, and again will be removed, the wavelength of the sound will once again be reduced (literally, smooth, if it draw on the graph).So it goes for the simple reason that the first sound of the siren a kind of "catch-up" machine, which shortens the distance between the troughs (ridges) waves and makes the tone of the above, and then, on the contrary, "running away", so that the wave as it were "smoothed".Actually, this is called the Doppler effect.
But we should not assume that the Doppler effect is somehow dry fact from the world of electrodynamics.This knowledge is widely used in modern radars sound, which is based on measurement of wave frequencies.And in the same way employees of traffic police determined the vehicle speed and other relevant services - speed aircraft, the flow of rivers, and so on. D. According to this principle works and burglar alarms that react to movement in the room.
discovery of Edwin Hubble
But perhaps the most significant discoveries related to the aforesaid effect is Hubble's law.Yet in 1929 the astronomer Edwin Hubble in the US turned his telescope at the starry sky.Observing distant galaxies, he found an interesting thing.Many of these galaxies are shrouded in an aura of some red haze.Like the sound of receding subject is heard us higher, so the color of the body seems to be receding reddish to the human eye.This literally means that the galaxies fly apart from us.Interestingly, the farther a galaxy is, the faster it is receding.This observation has contributed significantly to the most popular among modern astrophysicists idea of an expanding universe and the Big Bang as the beginning of it.