Helium gas is placed in a glass tube in a laboratory. An emission spectrum is produced.
Complete the sentences to explain the cause of the lines in the emission spectrum.
Use words from the list:
atoms, electrons, light, protons, sound
...................................... move from a higher energy level to a lower energy level and emit ...................................... .
There is a potential difference of 4500 V4500\text{ V}4500 V across the tube.
A charge of 0.08 C0.08\text{ C}0.08 C flows in the tube.
Calculate the energy transferred.
Use the equation: energy transferred=charge×potential difference\text{energy transferred} = \text{charge} \times \text{potential difference}energy transferred=charge×potential difference
A special power supply is needed to provide the high potential difference of 4500 V4500\text{ V}4500 V.
Describe one risk of using this power supply.
The figure below shows the emission spectrum for each of three different galaxies and a laboratory source on Earth.

The emission spectrum for each galaxy shows red-shift. Explain what is meant by the term red-shift.
Which galaxy in the figure is furthest from the Earth? Give a reason for your answer.
State which theory the spectra from each galaxy gives evidence for.