P1.6.4 The Expanding Universe

• Created on: 03-05-14 10:27
What is the Doppler effect?
The change of wavelength (and frequency) of the waves from a moving source due to the motion of the source towards or away from the observer.
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When the source moves towards the observer, what happens to the observed wavelength and frequency?
The observed wavelength decreases and the observed frequency increases.
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When the source moves away from the observer, what happens to the observed wavelength and frequency?
The observed wavelength increases and the observed frequency decreases.
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What do we mean by red-shift of a light source?
The red-shift of a distant galaxy is the shift to longer wavelengths of the light from it because the galaxy is moving away from us.
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How do we know the distant galaxies are moving away from us?
All the distant galaxies show a red-shift. The further away a distant galaxy is from us, the greater its red-shift is
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How does red-shift show that the universe is expanding?
The furthest galaxies are moving the fastest so everything is expanding outwards.
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How does red shift depend on speed?
The faster a distant galaxy is moving away from us, the greater its red-shift is.
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What did Hubble discover?
1. the light from distant galaxies was red-shifted. 2.the further a galaxy is from us, the bigger its red-shift is.
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What did Hubble conclude?
The distant galaxies are moving away from us. The greater the distance a galaxy is from us, the greater the speed is at which it is moving away from us.
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Other cards in this set

Card 2

Front

When the source moves towards the observer, what happens to the observed wavelength and frequency?

Back

The observed wavelength decreases and the observed frequency increases.

Card 3

Front

When the source moves away from the observer, what happens to the observed wavelength and frequency?

Card 4

Front

What do we mean by red-shift of a light source?

Card 5

Front

How do we know the distant galaxies are moving away from us?

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