Atomic line spectra
When a low pressure gas is excited (either by heat or electrical discharge) it produces light; neon signs are one use of this effect.
Most light is a mix of many different wavelengths (colours). By passing light through a diffraction grating it is possible to split it up into its constituent wavelengths as seen in the image below.
Most light is a mix of many different wavelengths (colours). By passing light through a diffraction grating it is possible to split it up into its constituent wavelengths as seen in the image below.
The bright lines (called spectral lines) indicate the particular wavelengths of light that are being emitted.
In 1885, Swiss mathematician Johann Balmer developed a formula that for the first time accurately predicted the visible wavelengths produced by excited hydrogen gas...
In 1885, Swiss mathematician Johann Balmer developed a formula that for the first time accurately predicted the visible wavelengths produced by excited hydrogen gas...
Where L = 3, 4, 5... and R is Rydberg's constant...
Following Balmer's work, more series of spectral lines were discovered in the infrared and ultraviolet spectrum. In 1888 Swedish physicist Johannes Rydberg devised a general formula that includes all of these series...
Where S = 1, 2, 3, ... and L = S+1, S+2, S+3, ...
e.g. if S = 1, then L = 2, 3, 4, ...
if S = 2, then L = 3, 4, 5, ...
if S = 3, then L = 4, 5, 6, ...
e.g. if S = 1, then L = 2, 3, 4, ...
if S = 2, then L = 3, 4, 5, ...
if S = 3, then L = 4, 5, 6, ...
Series nameLyman
Balmer Paschen Brackett Pfund Humphreys |
SpectrumUltraviolet
Visible Infrared Infrared Infrared Infrared |
S value1
2 3 4 5 6 |
L values2, 3, ...
3, 4, ... 4, 5, ... 5, 6, ... 6, 7, ... 7, 8, ... |