Frankfurt 2014 – scientific programme
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DD: Fachverband Didaktik der Physik
DD 4: Praktika und neue Praktikumsversuche 1
DD 4.3: Talk
Monday, March 17, 2014, 14:40–15:00, Casino 1.812
Visualizing fundamental physical phenomena using optical levitation — •Oscar Isaksson1,2, Magnus Karlsteen1, Mats Rostedt2, and Dag Hanstorp2 — 1Department of Applied Physics, Chalmers University of Technology, SE-412 96 Gothenburg, SWEDEN — 2Department of Physics, University of Gothenburg, SE-412 96 Gothenburg, SWEDEN
We will present an experiment in which optical levitation is combined with Millikan’s classical oil drop experiment. We have designed a system which can be used to demonstrate several fundamental physical phenomena using the bare eye as the only detector.
Electrically charged oil droplets are trapped and kept for up to eight hours in a vertically aligned and focused laser beam. The size, and hence the mass, of a trapped droplet is determined by producing a diffraction pattern with a horizontally aligned 633 nm HeNe laser. The vertical position of the electrically charged drop can be changed by applying an electric field. The change in position is measured by imaging scattered light onto a screen or a PSD. Excess electrons on the droplet can be removed by exposing it to an α-emitter. The final goal with the experiment is to demonstrate the quantization of charge by observing the change in position when single electrons are removed.
The total cost for the system is less than EUR 2000. It can therefore be made available at teaching institutes. The simplicity of the experiments will make it possible to move the set-up for demonstration at for example exhibitions or conferences.