Date: Tue Mar 31 12:34:04 2009 Back to Contents ------------------------------------------------------------------------

Author: Andy Dougherty

Subject: Re: LED photoelectric effect apparatus


On Mon, 30 Mar 2009, John Welch wrote:

> Hey all -
> we're making several homemade PE experiments using LED's, based on the
> article by Wayne Garver in the May 2006 Physics Teacher.

I looked at doing this too, but I made the "mistake" of trying to measure
the actual wavelength of the LEDs I had at hand, rather than relying on
the manufacturer's value. The LEDs had an extremely broad distribution of
wavelengths, easily verified by looking at one through a student
spectrometer. I've placed a graph at

This doesn't answer the question about the phototubes, of course, but does
make one wonder just what is actually being measured.

Andy Dougherty
Dept. of Physics
Lafayette College, Easton PA 18042

From Tue Mar 31 12:34:04 2009