What is the Doppler effect, applications and examples

Witnessing phenomena due to the Doppler effect in everyday life is much easier than we can imagine. But what is the doppler effect? We explain it below, with some of its applications and examples.What is the Doppler effect, applications and examples The Doppler effect is the physical phenomenon that refers to the ways in which a static observer perceives the frequency of an emission when the source is in movement. It was first analyzed by Christian Andreas Doppler in 1845. A passing ambulance, a swan swimming in a lake, the discharge of balls thrown by an automatic ball launcher, are examples where there is a source that emits a wave (sound, in the case of the ambulance siren) or something that can be compared to radiation (the crest of the wave or the thrown balls) and a stationary observer who observes the movement of these sources. As the source gets closer to the observer, the frequency of emission appears to increase. This happens because the wave fronts generated by the source (for example, the approaching ambulance) in turn approach the observer (or the listener, if we are talking about sound waves like those of the siren). of the ambulance is very useful to understand how the Doppler effect affects perception. In fact, a listener-observer perceives (apparent) variations corresponding to: higher frequency of the approaching wave fronts. lower frequency as the sound source moves away. The Doppler effect and the stars On the other hand, the Doppler effect has also been mentioned in regards to the universe and in particular it is applied to measure the speed at which stars move, but what relationship does this effect have and the speed of the stars?Let’s try to understand it: The emission of light from a star passes through the gas in its atmosphere. This gas absorbs a certain frequency of light, and in the resulting emission spectrum there will be a black band that represents the corresponding absorbed frequency.Thanks to the Doppler effect, for a moving star the displacement of this black band will occur in relation to that of the celestial body, and in particular, if the star moves away, there will be a shift towards the red, that is, towards the low frequencies (redshift). On the other hand, if the star gets closer, there will be a shift towards high frequencies, that is, towards blue (blushing). Taking as a reference the spectra of a star, that is, its absorption frequencies, it is possible to calculate its speed Finally, the redshifts of distant galaxies are interpreted as Doppler shifts due to the distancing of the galaxies themselves, which tells us that the universe is expanding.