In which type of spectrum would you expect to see bright lines on a dark background?

The correct choice is the emission spectrum, which is characterized by bright lines on a dark background. This phenomenon occurs when certain atoms or molecules in a gas emit light at specific wavelengths, which correspond to the energy differences between their electron energy levels. When this emitted light is passed through a prism, it produces a spectrum made up of bright lines (the emission lines) against a dark background.

In an emission spectrum, each line represents a distinct wavelength of light emitted by the material, unique to each element. This allows scientists to identify the composition of the gas due to the characteristic pattern of the bright lines.

In contrast, an absorption spectrum consists of dark lines on a continuous background of light. This occurs when light passes through a cooler gas, where certain wavelengths are absorbed by the atoms, resulting in dark lines where those specific wavelengths are missing from the spectrum.

A reflection spectrum arises when light reflects off a surface, and a continuous spectrum displays a smooth gradient of colors without any gaps; neither of these would show bright lines against a dark background. Thus, the emission spectrum is the only correct choice that fits the described characteristics.