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The sound wave doppler effect
In daily life,we can have this kind of experience:when a listed sound of the train whistle after one observer,he will find the train whistle of tone changes from high to low.Why will happen this phenomenon?This is because the discretion of the tone is by sound waves of vibration frequency of different decision,if high frequency,tone sounds is high; And tone sounds is low.This phenomenon is called doppler effect,it is to use the discoverer kristian doppler name,doppler is Austrian physicists and mathematicians.In 1842 he first discovered this effect.In order to understand the phenomenon,need to examine the train is approaching constant speed,the sirens of sound in a spread of the law when.The result is sound waves wavelength shorten,like wave is compressed.Therefore,in a certain time intervals of transmission wave number increases,and this is why will feel tone change observer reasons of high; Instead,when the train to far away,the wavelength of sound waves change,like wave by drawing.Therefore,the voice sounds is low.
The light wave doppler effect
The light of the volatility has also will appear this kind of effect,it has been called the doppler-which cable effect.Because the French physicist ophir cable (1819 1896) in 1848 to independently from star explains the wavelengths,and points out that the use of this effect to the relative speed measuring star.Light waves of sound and the difference is,light waves frequency changes make the person feel is color change.If stars far away,the light spectrum line to red light direction,called red shift; If stars towards us movement,the light spectrum line is moving to the direction,called blue shift.
The wavelength of the radiation object because waves and the relative motion of the observer and produce change.In the movement of the front waves,wave be compressed,wavelength becomes short,are higher frequency (blue shift); When movement in waves behind,to have the opposite effect.Wavelength becomes longer,frequency become low (red shift).The higher the speed of the waves,the greater the effect of.According to wave red (blue) moving degree,can calculate the waves followed the observation direction of movement speed.
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