120 likes | 842 Views
The Doppler Effect. Shown by all types of waves. Properties of Waves. Waves are characterized by two numbers: Wavelength, l (size of the wave) Frequency, ν (number of waves/second) For sound waves, frequency more commonly called pitch For light waves, these are all related by:
E N D
Properties of Waves • Waves are characterized by two numbers: • Wavelength, l (size of the wave) • Frequency, ν(number of waves/second) • For sound waves, frequency more commonly called pitch • For light waves, these are all related by: • c = l ν • Where c is the speed of light • Longer l means Smaller ν
Electromagnetic Wave Electric Field Magnetic Field
The Doppler Effect • Shift in the observed wavelength when the source is moving relative to the observer. • Examples: • Sound Waves (Siren or Train Horn) • Light Waves • Amount of the shift and its sign depends on • relative speed of the source & observer • direction (towards or away)
Same Pitch Same Pitch Stationary Source
Doppler Effect in Sound Low Pitch (long waves) High Pitch (short waves)
The Doppler Effect in Light • Works same as it does for sound • Light moving awayfrom the observer Wavelength gets longer:REDSHIFT • Light moving towardsthe observer Wavelength gets shorter:BLUESHIFT
- v obs = c em Way to Measure Speeds • Observe the wavelength (obs) of a source with a known emitted wavelength (em) • The difference is directly proportional to the speed of the source, v: em