An Expanding Universe Redshift, Blueshift and the Doppler Effect
EMS Review • The shorter the wavelength, the higher the frequency • The longer the wavelength, the lower the frequency • Red wavelengths of light are longer than blue wavelengths of light • Star composition can be determined by the spectrum of the gases present
Doppler Waves • As an object moves away from you, the waves spread out. Wavelength gets longer and frequency decreases. • When dealing with light waves, we say that the object has red-shifted because the waves move towards the red end of the spectrum
Doppler Waves • As an object moves towards you, the waves bunch up. Wavelength gets shorter and frequency increases • We say that the object has blue-shifted because the waves move towards the blue end of the spectrum.
How can we tell that the universe is expanding? As an object moves away from you, the object’s spectrum of gases shifts to the red side of the spectrum