Christian Doppler
Picture of Christian Doppler
Image courtesy of the University of St. Andrews, Scotland
|
Christian Doppler was an Austrian mathematician who lived between
1803-1853. He is
known for a principle he proposed in 1842. This is now known as the Doppler Effect.
He thought that the pitch of a sound would be different if the source of the
sound was moving. He didn't get to test his hypothesis until 1845.
Doppler tested his hypothesis by using two sets of trumpeters. One set
was at a train station and one set was on an open train car. The train
car was pulled past the station. Both groups of trumpeters played the
same note but the notes didn't match. The frequency of the notes had
changed.
Later, a scientist named Fizeau went further with Doppler's work and
applied it to light, too. Doppler had only worked out his theory for
sound.
|
How could Doppler tell the frequency of the notes had changed?
Christian Doppler
Picture of Christian Doppler
Image courtesy of the University of St. Andrews, Scotland
|
Christian Doppler was an Austrian mathematician who lived between
1803-1853. He is
known for the principle he first proposed in Concerning the coloured
light of double stars in 1842. This principle is now known as the
Doppler
Effect. He hypothesised that the pitch of a sound would change if
the source of the sound was moving. He didn't test this hypothesis until
1845.
To test his hypothesis, Doppler used two sets of trumpeters: one set
stationary at a train station and one set moving on an open train car.
Both sets of musicians had perfect pitch and held the same note. As the
train passed the station, it was obvious that the frequency of the two
notes didn't match, even though the musicians were playing the same
note. This proved Doppler's hyphothesis.
Later, a scientist named Fizeau generalized Doppler's work by applying his
theory not only to sound but also to light.
|
How could Doppler tell the frequency of the notes had changed?
Christian Doppler
Picture of Christian Doppler
Image courtesy of the University of St. Andrews, Scotland
|
Christian Doppler was an Austrian mathematician who lived between
1803-1853. He is
known for the principle he first proposed in Concerning the coloured
light of double stars in 1842. This principle is what is now known
as the Doppler
Effect. He theorized that sound waves from a moving source would be
compressed or expanded, or that the frequency would change. This theory
wasn't tested until 1845.
In 1845, Doppler set up an experiment using two groups of trumpeters, all
who had perfect pitch. One group set up at a train station while the
other set up on a train car that was to be pull past the station. Both
groups were to play the same note and Doppler's theory stated that the
notes would be dissonant (that the frequencies would be different). This
turned out to be true; the notes were audibly different, even though both
groups of musicians were playing the same note.
Later, a scientist named Fizeau generalized Doppler's work by applying his
theory not only to sound but also to light.
|
How could Doppler tell the frequency of the notes had changed?
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