What makes phosphorescence last longer?Featured science projectScience project video

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Complexity level:
4
Project cost ($):
20
Time required:
1 hour to prepare, 10 hours for observation
Material availability:
You will need access to UV/infrared lamps
Safety concerns:

NA

Abstract

An ultraviolet light source (as opposed to other forms of light sources) will be able to make the glow of phosphorescence material last longer.

Hypothesis

The lamp that produces more ultraviolet light will be able to make the glow of phosphorescence material last longer.

Background

Phosphorescence

Phosphorescence occurs when energy in light waves is absorbed by a phosphorescent material and later released in the form of light, at a very slow rate. This slow release of light energy is what causes the glow-in-the-dark sticker to continue glowing over a period of time.

When ultraviolet light is absorbed by the phosphorescent material, electrons in the atom become"excited". These electrons will eventually return to their normal energy levels, gradually. It is during this gradual process of electron state"degradation", that the material is seen to glow.

Types of lamps

Different types of lamps (mentioned below) are used to simulate different bands of light in the spectrum.

Infrared lamp - consists mainly of infrared light. Most of the infrared energy is lost as heat.

Incandescent lamp - emits a large percentage of infrared light

Florescent lamp - emits more ultraviolet light than the incandescent lamp

Ultraviolet lamp - consists mainly of ultraviolet light 

Scientific Terms

Phosphorescence, ultraviolet, infrared

Materials

The materials required for the experiment:
3 pieces of glow-in-the-dark stickers

  • 1 infrared lamp
  • 1 incandescent lamp
  • 1 florescent lamp
  • 1 ultraviolet lamp
  • 1 stopwatch
  • 1meter-long ruler 

Procedure

  1. For this experiment, the independent variable is the type of lamp used. The dependent variable is the time expired before for the stickers stop glowing.The constants (control variables) are the legth of time of exposure to the lamps, the power/output ratings of the lamps and the distance of the lamps from the sticker.
  2. This experiment must be performed in a dark room.
  3. The 3 pieces of glow-in-the-dark stickers are kept covered in a dark room. First the ultraviolet lamp is placed 1 meter directly above the stickers. The lamp is switched on, the cover over the sticker removed and the stopwatch started.
  4. The lamp is kept on for only 1 minute. The stopwatch is kept running to record the time taken for the sticker to stop glowing. The results are recorded in the table below.
  5. The glow-in-the-dark stickers are kept covered for another 10 minutes.
  6. Procedures 3, 4 and 5 are repeated using the incandescent lamp, florescent lamp and finally, the ultraviolet lamp. 

Observation

The glow-in-the-dark stickers will continue glowing longest and brightest after absorbing light from the ultraviolet lamp.

phosphorescence experiment results
The stickers will stop glowing sooneset after absorbing light from the infrared lamp. 

Conclusion

The hypothesis that glow-in-the-dark stickers will continue glowing the longest after the ultraviolet light and stop glowing the fastest after the infrared light is proven to be true. Infrared light and the incandescent light generate more heat and are in the lower frequency side of the light spectrum. The florescent lamp, mineral lamp and ultraviolet lamp generate light in the higher frequency spectrum. These lamps generate more ultraviolet light which is absorbed by the atoms.

The luminance of the phosphorescence material is popular among children toy and is also used in designing T-shirts. It can also be used as source of temporary light during sudden blackouts. Traffic police, road side workers and motorist also wear jackets with phosphorescence material coatings for safety and to be seen at night. 

Also consider

The experiment can also be done using a luxmeter to measure the illuminance of the stickers.

How will the results be if different type of phosphorescent material is used? (i.e. zinc sulfide) 

References

  • http://en.wikipedia.org/wiki/phosphorescence

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