29.1 Exercise 1

The visible spectrum of sunlight shows a range of colors from red to violet. This spectrum has numerous dark lines spread throughout it. Noting that the surface of the Sun is much cooler than the interior, so that the surface is comparable to a cool gas through which light passes, which of the following statements correctly explains the dark lines?

1. The cooler, denser surface material scatters certain wavelengths of light, forming dark lines.
2. The atoms at the surface absorb certain wavelengths of light, causing the dark lines at those wavelengths.
3. The atoms in the Sun’s interior emit light of specific wavelength, so that parts of the spectrum are dark.
4. The atoms at the surface are excited by the high interior temperatures, so that the dark lines are merely wavelengths at which those atoms don’t emit energy.