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This experiment is one of the experiments
of course 6 in the second year of the undergraduate student lab
at the Vrije Universiteit Amsterdam (VUA). (see Overview of Students Laboratories).
The students perform this experiment in 4 afternoons in the lab.
They are supposed to spend 8 hours for preparation and writing
the report.
Schedule for guidance
and students activities:
First 4 hours
in the lab:
Students read parts of the relevant topics. Students have to
align the experimental set-up themselves. If they do not succeed
to get an appropriate signal within 2 hours, the tutor should
align the set-up. Students explore the various possibilities
for investigations, i.e. profile of flow, the shape of the signal
(= the velocity distribution at different positions in the tube).
Problems to tackle:
- detection of the two crossing laser beams resulting in a bad
signal to noise ratio, because only the scattered light will
give the required information.
- Interpretation of the signal of the frequency-analyser (to
link theoretical concepts to the real results)
- Choice of the angle between the two crossing laser beams.
- Calibration of the set-up with a rotating thread. In case of
a bad alignment Fresnel fringes will cause a 'strange' result:
the frequency-analyser gives the wrong frequency.
Second 4 hours in the lab:
Students choose the experimental problem they will investigate.
Formulating hypothesis and expectations. Tutor helps the students
to clarify the used concepts and to link theory to practice.
Calculation and interpretation of preliminary results.
Preparing work plan.
Third 4 hours in the lab:
Work plan discussion between students and tutor. Determination
of definite experimental problem and planning of activities.
Fourth 4 hours in the lab:
Final measurements. Interpretation of results.
Homework:
Writing report.
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