crossigma.blogg.se - Atomic emission spectrum vs continuous spectrum

A glowing gas produces bright lines on a dark background at wavelengths or colours characteristic of the chemical components of the gas (an emission spectrum).įurther investigation by Kirchoff and Bunsen allowed them to conclude that the lines produced in the absorption and emission spectra were characteristic of the atoms that were heated or that the light passed through.

If a gas exists between the light source and the spectroscope, light is absorbed from the continuous spectrum at wavelengths or colours characteristic of the chemical components of the gas (an absorption spectrum).

A continuous colour spectrum is produced by glowing solids or dense gaseous bodies (a continuous black body spectrum).

Spectroscopy is the study of the electromagnetic spectrum and how electromagnetic waves interact with matter. Gustav Kirchhoff and Robert Bunsen used Bunsen’s burner to burn elements and clearly describe the cause of these spectral lines in 1859. This results in some parts of the spectrum being more intense than others in producing the colours that we see. The molecules absorb some frequencies and reflect others. Some of the wavelengths are absorbed by molecules in the material we are looking at. For example, you may look at a red book, however, what you are observing is a combination of some specific wavelengths which combine to ‘appear’ red. Often what we see in reflected light is the combination of colours that reflect. Other colours that we do not see are absorbed by the object. When it reflects, it shows the colours that we see when we look at the object. What we see when we look at an object is due to sunlight reflecting off a surface into our eyes.

Sunlight arrives as a nearly white light to our eyes. Incandescent sources present a continuous spectrum, with bands greatly broadened on account of the higher temperatures, whereas fluorescent sources are ‘spiky’ with discrete emissions at narrow wavelength bands. The spectra of incandescent and fluorescent lights differ. In household use, fluorescent lights operate on 15% of the power for an equivalent incandescent light. They are more expensive than an incandescent globe, but this is offset by lower running costs and a longer operating life. This enables them to convert more of the electrical energy into light energy and still remain cool to touch. This is the basis on which Fluorescent lights operate.įluorescent lights are more efficient than incandescent lights because they emit less energy in the infrared range. The ultraviolet light excites the phosphor, which then emits light over the entire visible spectrum. The inside of the glass is coated with a material called a phosphor. The current excites electrons in the gas and as they return to their ground state they emit light in the ultraviolet range. Compare this with the ‘white’ light from an LED globe which is more evenly distributed across the visible spectrum.ĭischarge tubes contain a low-pressure gas through which a current is passed. Incandescent globes produce a ‘warm’ light which has a yellow tone to it due to the spectrum emitted from it being ‘heavy’ in the shorter wavelengths of yellow/orange/red. There is a sharp drop of light in the ultraviolet, at wavelengths shorter than 400nm. The visible spectrum is between about 400 nm and 750 nm, so radiation longer than 750nm is invisible infrared EMR. Some of the light produced is in the infrared part of the spectrum that is invisible to human beings but is detected as heat. This range of wavelengths from the incandescent globe is a continuous spectrum. This results in the production of electromagnetic radiation at a range of wavelengths. Observing Spectra of Discharge Tubes, Reflected Sunlight and Incandescent FilamentsĪn incandescent light bulb produces light by heating a metal filament to a very high temperature. Violet refracts the most and red the least. Different wavelengths of light are refracted in different amounts, resulting in the light being dispersed, revealing its colours.

Light entering the prism is refracted towards the normal to the surface. Spectroscopes disperse light into its constituent colours and wavelengths by passing it through a prism. It was discovered that the solar spectrum was not continuous but was crossed by a number of black lines. The spectroscope was invented in an effort to explore the spectrum in more detail. Isaac Newton was the first to observe that a prism could disperse sunlight into a spectrum of colours.