3B Scientific SW Ultrasonics Set (115 V, 50__60 Hz) - Manual (Page 8)

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7. Experiments
7.1 Lloyd’s mirror
Fig. 4 Reflection from Lloyd’s mirror
Required:
1 Electronics board and plug-in power supply
1 Ultrasonic transmitter, 40 kHz
1 Microphone probe
1 Reflector
1 BNC/4-mm cable
Additionally required:
1 ESCOLA 10 multimeter
1006810
• Connect the supplied plug-in transformer to
provide power to the equipment.
• Connect the ultrasonic transmitter to Gen-
erator G1.
• Connect the microphone probe to channel A
and set it up some distance in front of the
transmitter.
• Connect the output of the channel to the
multimeter (measuring range: AC, 10 V).
• Turn on the high-pass filter by means of
switch S1 (
) and set switch S2 to .
• Set up the reflector parallel to the main
beam.
• Change the distance of the reflector from the
main beam and observe the maxima and
minima in the measured sound amplitude.
Note: If the distance between the plane between
the transmitter and receiver and reflecting sur-
faces such as the base plate is equal to certain
specific values, then the direct beam and the
one reflected from the surface may be superim-
posed in such a way that destructive interfer-
ence ensues. With Lloyd’s mirror it is possible to
determine the minimum distance at which this
effect occurs. The effect does not occur at all if
the transmitter and receiver are set up so close
together on the base plate that they are nearer
to each other than this minimum distance.
7.2 Reflection from a convex mirror
Fig. 5 Reflection of a diverging sound beam by a
convex mirror
Required:
1 Electronics board and plug-in power supply
1 Ultrasonic transmitter, 40 kHz
1 Ultrasonic pen with holder
or
1 Microphone probe
1 Convex mirror
1 Absorber
1 BNC/4-mm cable
Additionally required:
1 ESCOLA 10 multimeter
1006810
• Connect the supplied plug-in transformer to
provide power to the equipment.
• Connect the ultrasonic transmitter to Gen-
erator G1.
• Connect the ultrasonic pen, or alternatively a
microphone probe, to channel A and set it
up some distance in front of the transmitter.
• Connect the output of the channel to the
multimeter (measuring range: AC, 10 V).
• Turn on the high-pass filter by means of
switch S1 (
) and set switch S2 to .
• Set up the convex mirror and point the
transmitter towards it.
• Set up the reflector parallel to the direct
beam.
• Find the optimum position for the receiver by
using a geometric construction and position
the ultrasonic pen at that point.
• Move the ultrasonic pen until the received
signal is at a maximum.
Note: The alignment of the receiver and trans-
mitter with the convex mirror is comparable to a
domestic satellite dish.