Dopplerová

The Doppler effect, often referred to as Dopplerová in some contexts, describes the change in frequency or wavelength of a wave in relation to an observer who is moving relative to the wave source. It is named after Austrian physicist Christian Doppler. When the source of the waves is moving towards the observer, the observer perceives a higher frequency and shorter wavelength. Conversely, when the source is moving away from the observer, the perceived frequency is lower and the wavelength is longer. This phenomenon applies to all types of waves, including sound waves, light waves, and electromagnetic waves.

In the case of sound waves, the Doppler effect is commonly experienced. For instance, the pitch of a siren from an ambulance sounds higher as it approaches and lower as it recedes. This is because the sound waves are compressed as the source moves towards the observer, leading to a higher frequency (higher pitch), and stretched out as it moves away, resulting in a lower frequency (lower pitch).

The Doppler effect has numerous important applications in science and technology. In astronomy, it is used to determine the motion of stars and galaxies. The redshift of light from distant galaxies indicates that they are moving away from us, a key piece of evidence for the expansion of the universe. Conversely, blueshift indicates movement towards the observer. In medicine, Doppler ultrasound uses the Doppler effect to measure blood flow by detecting the frequency shift of sound waves reflected by moving blood cells. Radar systems also utilize the Doppler effect to measure the speed of objects, such as aircraft or vehicles.