Final answer:
The dark absorption lines in the Sun's visible light spectrum are caused by photon absorption in its cooler outer atmosphere, creating Fraunhofer lines that indicate the presence of specific elements and help determine the Sun's chemical composition.
Step-by-step explanation:
The dark absorption lines in the visible light spectrum of the Sun are caused by photon absorption, which takes place in the Sun's cooler outer atmosphere. These lines are indications of the presence of certain chemical elements absorbing specific wavelengths of light, causing the lines to appear dark against the continuous background spectrum. The phenomenon is named after German physicist Joseph von Fraunhofer and the lines are thus called Fraunhofer lines.
Astronomers use these absorption lines to determine the chemical composition of the Sun and other stars. Because the rest of space between Earth and the Sun is largely empty, the atoms involved in the absorption process are located in the Sun's atmosphere, which is cooler and thinner than its interior. Understanding the composition of the Sun's atmosphere serves as an indicator of the Sun's overall makeup.
The relationship between the dark lines of an absorption spectrum and the colored lines of an emission spectrum is that the wavelengths absorbed in the former correspond to those emitted in the latter. This allows scientists to identify which chemical elements are present in celestial bodies.