The figure below shows part of the emission spectrum of visible radiation emitted by hydrogen gas in a star in a distant galaxy.
The galaxy is moving away from the Earth at a speed of 
.
Explain how the positions of the lines in the emission spectrum seen by an observer on the Earth differ from the positions shown in the figure above.
On the figure above, draw the three lines in possible positions in the spectrum seen by the observer.
The lines in the figure above correspond to electron transitions down to the energy level 
. One of the lines represents emitted radiation of wavelength 
.
Calculate the energy of a photon of this radiation.
Determine the energy, in 
, of the energy level from which the electron transition originates to cause the emission of this radiation.
Determine the wavelength, in 
, of this radiation as detected by the observer on the Earth.
A value for the Hubble constant is 
. Determine the distance of the galaxy from the Earth.
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