Video: Watch this demo
Description: With this demonstration, each student gets a diffraction grating that they use to view the emission lines of different sources.
The above pictures show what can be expected when viewing each tube though a diffraction grating.
Equipment:
- High voltage discharge tube power supply
- Three different discharge tubes
- Clear incandescent light bulb
- VariAC
- Many small diffraction gratings
- VariAC to banana plug cable
Setup Procedure:
- Connect the light bulb to the VariAC. Set to about 120VDC
- Be careful when handling the discharge tubes, as they are fragile (as are their cables).
Demonstration Procedure:
- Have students come and pick up a diffraction grating.
- Start by showing students the incandescent lite. Turn on the VariAC and turn off all other lights.
- Have students view the light with the diffraction grating. Note that almost all the frequencies of visible light are present.
- Turn off the VariAC and connect one of the discharge tubes to the discharge tube power supply. Go gentle with the cables, they are fragile.
- Turn on the power supply and have students view the new source with their gratings.
- There are three discharge tubes: Neon, Mercury, and Hydrogen. You can expect students to see the emission lines similar to the above pictures.
- Turn off the power supply.
- Repeat with the other two discharge tubes. Note the new emission lines characteristic of each gas.
- When finished, turn off the power supply.
- Have students turn in their diffraction gratings into the plastic bin when done.
Note: The wires are very delicate. The room must be dark so students don’t view other lights in their diffraction grating.
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