Final answer:
The line spectrum observed when light from excited atoms is passed through a prism signifies discrete photon energies unique to each element, with each line representing a specific wavelength.
Step-by-step explanation:
When the light emitted by electronically excited atoms passes through a prism, a line spectrum is observed, which signifies the discrete energies of the photons emitted by the atoms. These discrete lines correspond to specific wavelengths of light that the atoms release upon returning from an excited state to a lower energy state. Unlike the continuous spectrum produced by a hot object that emits a full rainbow of colors, a line spectrum consists of individual lines each representing a particular wavelength.
For example, hydrogen atoms, when excited, will emit light that, when passed through a prism, reveals a line spectrum with distinct wavelengths corresponding to the blue, green, red, and violet parts of the visible spectrum. Each element has its own unique characteristic line spectrum, which can be used to identify the presence of that element in a sample. This is fundamental to the field of spectroscopy and is valuable for studying stellar spectra and understanding the composition of distant stars.