The Photoelectric Effect - A Simple Experiment w/ UV Photons

How can light discharge the tinsel?! Try this experiment! Tinsel, a negatively charged PVC pipe, an aluminum cake pan and an ultraviolet light (germ sanitizer) are used to demonstrate the photoelectric effect.




In a nutshell, the photoelectric effect is the emission of electrons when a surface is exposed to photons of sufficient energy. Note that the effect is frequency dependent. Electrons will be emitted if the photon frequency equals or exceeds the threshold frequency for the metal. One could shine a 100 watt Helium Neon laser on the aluminum pan without discharging the tinsel. In contrast, when UV photons strike the pan, they are quickly absorbed and readily release electrons.

A few tips: PVC pipe works great for giving the tinsel a static charge. Note, however, that not all tinsel will work properly. It must be electrically conductive and light weight. If the tinsel continues to cling to the PVC pipe, it is probably not conductive enough. See "tips and secrets" at the end of the video for further details. Note that this experiment works ONLY when the tinsel is given a negative charge. For best results, place the apparatus on top of an insulating material, such as a thick sheet of plexiglass or rubber. Also note that it was necessary to lightly scrub the surface of the aluminum pan, to expose the bare metal.

Going further: Try other metals. Try electrolytes, coatings, various frequencies of light. Ponder how you might use this knowledge to design a solar cell. Share your discoveries!

Caution: Overexposure to UV radiation can be harmful to humans! Follow simple safeguards.

Music: "Deliberate Thought" courtesy of Kevin MacLeod

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[glily2]

great effort,experiments tell much more than the theory...if the metal is positively charged and then is exposed to UV light,what will happen???

[ElectricVentures]

@glily2 Try it! Would the emissions of electrons discharge the tinsel if it was positively charged?

[rockmn24]

Sorry for the double comment. My internet is quite slow.

[ElectricVentures]

@rockmn24 No problem! "Live long and prosper!" :-) 

[rockmn24]

I got a perfect score, my friend! I was graded 30/30, 30/30, 30/30, and 33/30, respectively.

[ElectricVentures]

@rockmn24 Well done! Glad this video was of use. :-)

[paddy110287]

@glily2 The electrons that tried to get away would be brought straight back to the positive charge, nice video also

[Shelbatron1000]

neat

[rockmn24]

@ElectricVentures Thank you, my friend! I got a perfect score! The judges graded me 30/30, 30/30, 30/30, 30/30, and 33/30., respectively.