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Re: [Phys-l] Hewitt's three answers



P.S.

Looking at the Figure 1 again I think that the amplitudes of fluctuations would be much smaller that 22%, if one was measuring temperatures, rather than light intensities. Yes I am thinking about the T^4 law. The tungsten spiral filament probably behaves nearly as if it were an ideal black body.

The challenge is how to measure the temperature without depending on radiation. What about plotting the R(t), where R is the resistance = v/i? The dependence of R on temperature is nearly linear, in a narrow range of T.

Ludwik
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On Mar 29, 2012, at 10:25 PM, Ludwik Kowalski wrote:

Thank you for sharing, Mike.

Ludwik
==================================================

On Mar 29, 2012, at 10:16 PM, Edmiston, Mike wrote:

When I teach the linear electronics course at Bluffton University, I have the students connect a phototube to an operational amplifier configured as a current-to-voltage converter. We connect the output of the opamp to an oscilloscope and view the flicker of various light sources.

I didn't have any records of this, so this afternoon I ran back to the lab, made the circuit, and recorded some data with a digital oscilloscope.

I did it really fast and didn't take time to adjust the oscilloscope for maximum performance, but the pictures are clear and show exactly what those of you following this thread need to see.

I assembled the pictures with a little write-up into a PDF file, and you can observe or download the file from the following link.

www.bluffton.edu/~edmistonm/Flicker.pdf



Michael D. Edmiston, PhD.
Professor of Chemistry and Physics
Chair, Division of Natural and Applied Sciences
Bluffton University
Bluffton, OH 45817
Office 419-358-3270
Cell 419-230-9657

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_______________________________________________
Forum for Physics Educators
Phys-l@carnot.physics.buffalo.edu
https://carnot.physics.buffalo.edu/mailman/listinfo/phys-l