PASCO SF-9405 User Manual
Instruction Sheet
for the PASCO
Model SF-9405
RESONANCE WIRE LOOP
Introduction
The PASCO Wire Loop demonstrates standing waves on a
closed circular wire. It can also be used to show the phenomena of de Broglie matter waves.
Theory
In 1913, Bohr formulated the well-known planetary model
of the atom. In this model, an electron orbiting farther from
the nucleus is in a higher energy state than one in a closer
orbit. Radiation of light from from the electron takes place
when the electron moves from a higher energy level to a
lower energy level. This model solved the mystery of atomic
spectra.
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However, the fact that electrons may occupy only certain
energy levels confounded Bohr and other investigators. The
electron was considered to be a particle that could orbit
around its nucleus at any radial distance (depending on its
speed). But this doesn't happen. The mystery of discrete
energy levels can be understood by considering the electron
to be not a particle, but a matter wave.
Louis de Broglie presented the idea of matter waves in 1924.
He suggested that a wave was associated with every particle.
The wavelength of a matter wave is inversely proportional to
the particle's momentum. A Bohr orbit exists where an
electron matter wave reinforces itself constructively. In this
view, the electron is thought of as though its mass and
charge are spread out into a standing wave surrounding the
atomic nucleus. The wavelength of the matter wave must fit
evenly into the circumferences of the orbits. The innermost
orbit has a circumference of one electron wavelength, the
second orbit has a circumference of two electron wavelengths, and so on. For each orbit the electron has a unique
speed, and therefore a unique wavelength.
The PASCO Wire Loop will have standing waves at discrete
frequencies, each one corresponding to a unique wavelength.
Additional Equipment Required:
• Mechanical Driver, PASCO Model SF-9324
• Function Generator with Amplifier, PASCO Model
PI-9587A or PI-9598
Equipment Setup
• Support for holding the mechanical driver approximately 40 cm above the table top.
Setup Procedure
1. Loosen the screw on the banana plug which holds the two
ends of the loop. Adjust the banana plug perpendicular to the
plane of the loop as shown in the Equipment Setup figure.
Tighten the screw.
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Setup Procedure (cont.)
2. Mount the Mechanical Driver (PASCO Model SF-9324) on
a stand with the drive shaft horizontal and about 40 cm above
the table top. See Equipment Setup figure.
3. Insert the banana plug into the Mechanical Driver shaft.
4. Connect the Mechanical Driver to a function generator
capable of driving a speaker (The PASCO PI-9587A Digital
Function Generator/Amplifier or PI-9598 Student Function
Generator are excellent for this purpose.)
5. Start driving the Mechanical Driver at about 5 Hz with
approximately 1 mm of amplitude and slowly increase the
frequency.
6. As the frequency is increased the wire will begin to vibrate
in various modes with an odd number of anti-nodes present.
These nodes are a very graphic demonstration of how electrons
can have a resonant frequency as they orbit the nucleus.
Limited Warranty
PASCO scientific warrants this product to be free from
defects in materials and workmanship for a period of one
year from the date of shipment to the customer. PASCO will
repair or replace, at its option, any part of the product which
is deemed to be defective in material or workmanship. This
warranty does not cover damage to the product caused by
abuse or improper use. Determination of whether a product
failure is the result of a manufacturing defect or improper
use by the customer shall be made solely by PASCO
scientific. Responsibility for the return of equipment for
warranty repair belongs to the customer. Equipment must be
properly packed to prevent damage and shipped postage or
freight prepaid. (Damage caused by improper packing of the
equipment for return shipment will not be covered by the
warranty.) Shipping costs for returning the equipment, after
repair, will be paid by PASCO scientific.
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