The absorption lines for a cool thin gas are identical in color and energy to the emission linesof the same gas if hot enough to glow.

Question

Quizplus · Accepted Answer

This statement is true. The color and energy of both absorption and emission lines depend on the transitions between energy levels in the atoms/molecules of the gas. These transitions result in the absorption or emission of specific wavelengths of light. Therefore, if a cool thin gas absorbs certain wavelengths of light, those same wavelengths will be emitted by the gas if it is heated to a temperature where it glows, resulting in identical absorption and emission lines. This is known as Kirchhoff's law of thermal radiation, which states that a material that absorbs light at a certain wavelength will also emit light at that same wavelength if heated to a high enough temperature. Thus, the absorption lines for a cool thin gas and the emission lines for the same gas at a high temperature will be identical in color and energy.

The Absorption Lines for a Cool Thin Gas Are Identical