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When in doubt, think about only one velocity being other than zero. Source moving away, frequency drops- positive. Source moving toward you, frequency rises- negative, You move toward source, frequency rises- positive. You move away from source, frequency drops- negative.k121212 said:
The Doppler Effect is the change in frequency or wavelength of a wave in relation to an observer who is moving relative to the wave source.
The Doppler Effect is commonly observed with sound waves, where an observer moving towards a sound source will perceive a higher frequency (and shorter wavelength) of the sound, while an observer moving away from the sound source will perceive a lower frequency (and longer wavelength).
The formula for calculating the Doppler Effect is: f' = f (c +/- v0) / (c +/- vs), where f' is the perceived frequency, f is the actual frequency, c is the speed of the wave, v0 is the velocity of the observer, and vs is the velocity of the wave source.
The Doppler Effect also applies to light waves, where an observer moving towards a light source will perceive a higher frequency (and shorter wavelength) of the light, while an observer moving away from the light source will perceive a lower frequency (and longer wavelength). This is commonly observed with astronomical objects, such as stars and galaxies, and is used to determine their relative motion.
The Doppler Effect has various practical applications, including in radar systems, where it is used to determine the speed and direction of moving objects. It is also used in medical imaging techniques, such as ultrasound, to measure blood flow and detect abnormalities. Additionally, it is used in astronomy to study the motion and properties of celestial objects.
