<Tr> <Td> 2 . </Td> <Td> Source approaching stationary observer with speed v </Td> <Td> n / x = a / (a - α) </Td> <Td> f' / f = c / (c-v) </Td> </Tr> <P> § 4 Doppler provides imaginary examples of large and small frequency shifts for sound: </P> <Table> <Tr> <Td> v = - c </Td> <Td> f' = 0 </Td> <Td> frequency shift down to inaudibly low tones </Td> </Tr> <Tr> <Td> v = - c </Td> <Td> f' / f = 0.5 </Td> <Td> frequency shift down over 1 octave, still audible . </Td> </Tr> <Tr> <Td> v = + c </Td> <Td> f' / f = ∞ </Td> <Td> frequency shift up to inaudibly high tones </Td> </Tr> <Tr> <Td> v = 40 m / s </Td> <Td> C to D </Td> <Td> note C shifting to D . </Td> </Tr> <Tr> <Td> v = 5.4 m / s </Td> <Td> quarter note </Td> <Td> threshold for best observers with absolute hearing </Td> </Tr> </Table> <Tr> <Td> v = - c </Td> <Td> f' = 0 </Td> <Td> frequency shift down to inaudibly low tones </Td> </Tr>

Über das farbige licht der doppelsterne und einiger anderer gestirne des himmels