Uploaded June 2021 | Updated September 2026, 6 hours ago
The photoelectric effect concerns the emission of electrons by ultraviolet light.
In this video I give a quick demonstration of this phenomenon using a gold leaf electroscope, a zinc pate, an EHT power supply, a high intensity (visible) light source and an ultraviolet lamp.
I start by giving the zinc a negative charge (so that it has an excess of electrons) and expose it to first the visible light and then the uv light.
Next I give the zinc a positive charge (so that it has too few electrons), repeating the exposure.
This second part of the demonstration (using the positive charge) is rarely performed by teachers, in my experience, and yet (in my opinion) is a very important part of the demonstration. Many people forget the importance, at times, of noting what fails to happen alongside what does happen.
The photoelectric effect concerns the emission of electrons by ultraviolet light.
In this video I give a quick demonstration of this phenomenon using a gold leaf electroscope, a zinc pate, an EHT power supply, a high intensity (visible) light source and an ultraviolet lamp.
I start by giving the zinc a negative charge (so that it has an excess of electrons) and expose it to first the visible light and then the uv light.
Next I give the zinc a positive charge (so that it has too few electrons), repeating the exposure.
This second part of the demonstration (using the positive charge) is rarely performed by teachers, in my experience, and yet (in my opinion) is a very important part of the demonstration. Many people forget the importance, at times, of noting what fails to happen alongside what does happen.
