Differentiating Emission Spectrum of Gas in a Discharge Tube from White Light Spectrum
How does an emission spectrum of a gas in a discharge tube differ from a white light spectrum?
What does the emission spectrum of a gas in a discharge tube consist of?
What is the white light spectrum comprised of?
What happens when an electrical discharge is passed through a gas at low pressure?
Answer:
The emission spectrum of a gas in a discharge tube is comprised of distinct lines of specific wavelengths, called a line spectrum, representing discrete energies emitted by atoms, versus the continuous spectrum of white light that encompasses all wavelengths with no gaps.
When an electrical discharge is passed through a gas at low pressure, the energy is absorbed by the gas atoms. As they relax back to their ground state, they emit photons at specific energies, resulting in distinct lines in the spectrum, known as a line spectrum. This is in contrast to a white light spectrum, where a hot object emits continuous spectrum containing all wavelengths without any gaps.
For instance, hydrogen gas in a discharge tube produces a distinct series of lines known as the Hydrogen spectrum, which can be predicted by an equation due to its simplicity compared to other elements. The emitted light from a gas is a set of discrete energies, exemplified when passing light from hydrogen gas through a prism and observing four visible wavelengths. Conversely, incandescent bulbs emit light due to being heated and produce a continuous spectrum, showing a blend of all visible colors with no distinct lines.