Explain how the line positions in the emission spectrum recorded by an observer on Earth are different from those shown in Fig. 8.1.
On Fig. 8.1, draw the three lines in positions that could be seen in the spectrum observed by the observer.
The lines in Fig. 8.1 are due to electron transitions to the energy level $-3.40\,\text{eV}$. One of the lines shows emitted radiation with wavelength $488\,\text{nm}$. Calculate the energy of a photon of this radiation.
Determine the energy, in $\text{eV}$, of the energy level from which the electron transition starts and which produces the emission of this radiation.
Determine the wavelength, in $\text{nm}$, of this radiation as observed on Earth.
A value for the Hubble constant is $2.3 \times 10^{-18}\,\text{s}^{-1}$. Determine the distance of the galaxy from the Earth.