Would you like to contribute lesson suggestions? Contact us. Through the looking glass Teaching Resources Even familiar demonstrations should be practised and safety-checked by individual teachers before they are used in a classroom. Individual teachers are responsible for safety in their own classes. SafetyĪvoid looking at the sun, lasers, or other bright sources. Note: to improve results, you can put a cardboard slit in front of the light sources but be very careful not to let the cardboard get too close to the bulbs, particularly the incandescent as it will be very hot. As you increase the temperature, making the filament hotter, all of the colours get brighter but the percentage of light in the blue and violet increases dramatically as expected for something approximating a blackbody.
When the filament is warm blue and violet are pretty much missing. Or put an old incandescent bulb on a dimmer to illustrate colour temperature and blackbody radiation.
Diffraction grating physics code#
With the compact fluorescent bulb you can see the visible part of the Hg bar code and the light produced by fluorescence, and the the LED you can see the driving light (far blue/violet), a fluorescence gap, and the fluorescence spectrum. Have a look at a compact fluorescent bulb and an LED bulb. These glasses are invaluable for investigating modern lighting technology. With this number in hand you can measure the wavelength of other lines in other spectra. Results agree well with the 500 lines/mm given on the glasses. The separation of the source from one of the observed D lines can be used to calculate sin θ in the formula The distance from the source is recorded. Looking at the discharge tube through the glasses students walk away from the source until the perceived D lines line up with the two marks. Mark two points about 3 m apart and place the sodium discharge tube in the centre. For example, the bright sodium D line (589 nm) can be used to calculate the actual spacing of the glasses. Examples are displayed below.Īlthough a qualitative demonstration with these glasses is enormously useful in itself, quantitative measurements can be made as well. Increasing the distance between the observer and the light source will spread out the observed spectrum. The images above do not do justice to the visual observations. If possible face the light sources away from each other to prevent stray light affecting the observed spectra. The tubes will need to be covered so that only a small slit of light is exposed. These glasses are very inexpensive and are very useful. It is possible to do pretty good quantitative experiments with these glasses. This can be used to illustrate everything from “bar codes” for chemical elements to colour temperature to lighting technology and so on. The diffraction gratings separate the colours contained in a light source.
Diffraction grating physics portable#
The “bar code” for neon as seen through the glasses Portable Inexpensive diffraction grating glasses are used to observe the spectra of many light sources.
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