EuPhO 2026, experiment — Задача 1. Task E1: Probing the acoustic field (1.0 pts)

Experimental task Language: English · 1 т.

Условие

An acoustic levitator consists of transducers which convert an electrical signal into intense sound waves. The acoustic pressure of the resulting interference pattern can levitate small objects close to the nodes of the pattern.

Warning: Avoid short-circuiting the connections on the top and bottom of the levitator.

The tasks E1-E7 of this exam are designed to be independent of each other's results. You may skip tasks you are struggling with.

For the following tasks, consider only the nodes on the z-axis. For task E3 and onward, use only the centremost node. The Mode X switch on the electrical box (F), see Fig. 1, should be in position O.

Equipment

A. Two green Light Emitting Diodes (LEDs). Do not connect the LEDs to the power supply (G).

B. Individual transducer.

C. Metal frame with a levitator module and a red LED, which can be modeled as a point source.

D. Capture unit for collecting falling objects.

E. 2 hex keys for mounting and aligning the setup.

F. Electrical enclosure with switches LED and Mode X.

G. Power supply.

H. Banana cables.

I. Screen.

J. Tape.

K. Transparent ruler.

L. Metal net.

M. Tweezers.

N. 15 blue styrofoam beads.

O. Multiple white spherical beads of unknown material (⌀ 2.0 mm).

P. Multiple transparent spherical glass beads (⌀ 2.0 mm, $\rho_{\mathrm{glass}} = 2500\ \mathrm{kg\ m^{-3}}$).

Q. 3 different unknown liquids labelled I, II and III. They are all safe to touch with your hands, but should not be ingested.

R. 3 syringes.

S. 3 blunt end needles for the syringes (be careful!).

T. 2 clothes pegs.

U. Stop watch.

V. Lamp.

W. Power cord.

X. Piece of paper to dry the metal net (not in image).

If you suspect that a component has failed for some reason during the competition, inform the invigilator to get help.

To get familiar with the acoustic field, use the green LEDs (A) and the transducer (B) to construct a tool that emits light according to the local acoustic intensity. A transducer is a capacitor whose charge depends on the mechanical pressure applied to it.

Task E8: Intentional damage penalty (-0.5 pts)

All equipment and packaging is left on the table after the competition in working condition. For breaking components or packaging due to careless handling or failing to follow the warning in red text, a penalty will be applied. (-0.5 pts)

a) Draw a circuit diagram for your tool. [0,5 т.]

b) Use your tool to roughly estimate the distance between two adjacent antinodes on the $z$ axis in the centre of the levitator. [0,5 т.]

Решение

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Оригинал в Архива: eupho2026_experiment_problems.pdf · официални решения: eupho2026_experiment_solutions.pdf