Transcript Teacher`s Lab 03 (Working group)

Importance, relevance and the level of
students’ preparedness, before trying
on these experiments.
In this experiment, a ball with a
central rod magnet, rotates with
low friction on air cushion and acts
as model electron. Two pairs of
coils generate a constant magnetic
field B0 and an alternating
magnetic field B1. The axes of both
fields intersect perpendicularly at
the centre of the ball. The table is
slightly inclined to start the
electron gyroscope with an air
draught (Magnus effect). If the
direct magnetic field B0 acts on the
ball, a precision of the magnet axis
is observed. Precision frequency
increases with the intensity of B0.
With the second pair of coils and a
pole change over switch
(commutator), a supplementary
alternating field B1 is generated. If
the change of poles occurs at the
right phase, the angle between the
gyroscope axis and the direction of
the direct field is continuously
increased, until the magnetic axis
of the ball is opposed to the field
direction (spin flip).
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Comments
Expensive for schools to have
Since it is a demonstrative experiment, some
schools might like to have it in their Physics lab.
Students need a prior knowledge of
Zeeman effect
Energy quantum
Quantum number
Resonance
G – factor
Lande’ factor
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To demonstrate the phenomenon of “electron
spin resonance”.
Does not offer too much of student
participation.
Needs practice to actually demonstrate the
phenomenon involved.
In this
experiment, a
photocell is
illuminated
with
monochromatic
light of different
wavelengths.
Planck’s
quantum of
action, or
Planck’s
constant ‘h’, is
determined
from the
photoelectric
voltages
measured.
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Comments
Pricy indeed, as a school would like to have more
than one of the setup.
Beneficial for the students, as they can practice the
art of data collection and manipulation.
Students need a prior knowledge of
External photoelectric effect
Work function
Adsorption
Photon Energy
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To study voltage of the photo cell as a function
of the frequency of the irradiated light.
Definitely a good experiment, from the
students’ as well as the schools’ points of view.
In this
experiment,
cathode rays ( a
stream of
electrons) are
subjected to a
magnetic field
and the
corresponding
trace is viewed on
a fluorescent
screen. This
exercise is helpful
to study how
“Lorentz force”
works.
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Comments
Very good demonstrative experiment.
Can be used to demonstrate so many other
phenomenon, like thermionic emission and
Lissajous figures. (We tried but could not handle
the function generator)
Students need a prior knowledge of
Thermionic emission
Lorentz Force
Magnetic field around a solenoid (coil)
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To demonstrate phenomenon like
Thermionic emission
Lorentz force
Oscilloscope principals
Wave forms
Lissajous figures (improvisation required)
An useful experiment for students, teachers
and schools
Can be improvised to an exercise experiment
In this experiment,
electrons are
accelerated in an
electric field and
enter a magnetic
field at right angles
to the direction of
motion. The specific
charge of the
electron is
determined from the
accelerating voltage,
the magnetic field
strength and the
radius of the
electron orbit.
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Comments
Relatively expensive.
Certainly a good experiment to have in a well
equipped laboratory.
Students need a prior knowledge of
Cathode rays
Lorentz force
Electron in crossed field
Electron mass
Electron charge
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For the determination of specific charge of the
electron (e/m0) from the path of an electron
beam in crossed electric and magnetic fields of
variable strength.
In this experiment,
fast electrons are
diffracted from a
polycrystalline layer
of graphite.
Interference rings
appear on a
fluorescent screen.
The interplanar
spacing in graphite
is determined from
the diameter of the
rings and the
accelerating voltage.
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Comments
Relatively inexpensive.
Not safe for students to try their hands on.
The radius of rings do not match with the voltage most of
the times. So the readings are not easily reproducible.
Preparedness of your class in order to make the most of this
experiment
Bragg reflection
Debye – Scherrer method
Lattice planes
Graphite structure
Material waves
De – Broglie equation
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To measure the diameter of the two smallest
diffraction rings at different anode voltages.
To calculate the wavelength of the electrons
from the anode voltages.
To determine the interplanar spacing of
graphite from the relationship between the
radius of the diffraction rings and the
wavelength