Images & portions of this lab have been provide by Dr. Walt Volland, Bellevue Community College
is the analysis of light spectra and the way in which light interacts with
matter. When light is analyzed it is commonly separated into its component
colors. The light source is directed on a slit and the "beam" of
light is separated using a prism or grating.
The reason that the images are lines is that the light from the lamp is focused on a narrow slit. The illustration shows the separation of a light beam into its component colors.
|You can see the specific colors emitted by the light source. A white light (Tungsten lamp or white fluorescent lamps) source will give a spectrum like the one shown above. This is an example of a continuous spectrum, also know as the visible spectrum of colors.|
|Each color has a characteristic wavelength. The wavelength is the distance between the beginning and end of a complete cycle of the light wave or the distance from one crest to the next. The crest is the tallest part of a wave and the trough is the lowest point of a wave. All colors of light travel at the same speed, 300,000 kilometers/ second. The animation shows how a prism separates photons of red light from photons of blue light. The photons of different colors fall in different positions on the color spectrum. The position is determined by the wavelength.|
|Blue light has shorter wavelength in the range of 400 nm (4000 Ångstrom or 0.00000004 m)|
|Red light has longer wavelength and is lower in energy than blue light. The wavelength of red light corresponds to the range of 700 to 600 nanometers, (7000 Ångstrom or 0.0000007 meters).|
3 Types of Spectra
Spectrum- produced by a glowing solid, liquid, or gas under
certain conditions. This spectrum consists of a continuous set of emission
lines side by side, with no gaps, and appearing as a smooth transition of
all colors from red to violet.
2. Dark-Line Spectrum / Absorption Spectrum- produced when a cooler gas lies between the observer and an object emitting a continuous spectrum. The cooler gas absorbs specific wavelengths of radiation passing through it. This spectrum appears as a continuous spectrum of all colors with a number of gaps or dark lines throughout it.
3. Bright-Line Spectrum / Emission Spectrum- produced by a glowing gas which radiates energy at specific wavelengths characteristic of the element or elements composing the gas. This spectrum consists of a number of bright lines against a dark background. Different elements produce different spectra. These different spectra are called the atomic spectra and are unique enough to be thought of as a finger print of the element. See Part 2 below.
|Emission Spectroscopy - Identification of Elements|
Click on each element
name below to view its flame test.
Part 2 Emission line spectra for selected elements