Transcript waves - Net Start Class

12 Weeks to TAKS
Week 5
• Obj. 5: IPC 5A and 5B Demonstrate
wave types and their characteristics
through a variety of activities such
as modeling with ropes and coils,
activating tuning forks and
interpreting data on seismic waves.
Demonstrate wave interactions
including interference, polarization,
reflection, refraction, and
resonance within various materials.
• IPC 6F Investigate and compare
series and parallel circuits.
WAVES
By moving a rope regularly up and down, a
traveling or periodic wave is produced.
Waves transfer energy from one place to
by vibrating something up and down, or
back and forth.
A transverse wave is a wave in which
the particles of the medium are
displaced in a direction perpendicular
to the direction of energy transport.
. The
crest of a wave is the point on the
medium which exhibits the maximum amount
of positive or upwards displacement from the
rest position.
The trough of a wave is the point on the
medium which exhibits the maximum amount of
negative or downwards displacement from the
rest position
The amplitude of a wave refers to the
maximum amount of displacement of a a
particle on the medium from its rest
position. The amount of energy carried
by a wave is related to the amplitude of
the wave.
A longitudinal wave is a wave in
which the particles of the medium
are displaced in a direction parallel
to the direction of energy
transport.
• A compression is a point on a medium through
which a longitudinal wave is traveling which
has the maximum density. A region where
the coils are spread apart, thus maximizing
the distance between coils, is known as a
rarefaction. A rarefaction is a point on a
medium through which a longitudinal wave is
traveling which has the minimum density.
A tuning fork serves as a useful
illustration of how a vibrating
object can produce sound.
Characteristics of Waves:
a. Frequency – the number of complete waves
passing a point in space per second; depends
on the source
b. Wavelength – the distance from a point in
a wave to the next point that wave in the
same phase, often symbolized with l
(lambda)
By knowing the frequency of a wave and
its wavelength, we can find its velocity.
Here is the equation for the velocity of
a wave:
velocity = wavelength x frequency
or
v=lxf
• Light waves will always travel
in a straight line until they hit
a barrier. So whether its
traveling through air, water,
glass, diamond, or any
substance (or none at all),
light travels in a straight
path, until it encounters a
different medium.
All visible objects either emit light or reflect
light. When an object either emits light or
reflects it, the light travels in all directions
from the object. If viewed through a pinhole
the light rays encounter no different medium
so they travel
in a straight
line.
Wave Properties: Reflection
When a wave hits a
barrier, it will be
reflected depending on
the direction of the
barrier (normal). The
angle between the
incident wave and the
normal is the same as
the angle between the
normal and the
reflected wave.
• Reflections are commonly observed with
sound waves. Echos are reflected sound
waves. When you yell in a canyon, the sound
wave travels through the medium (air in
this case), reflects off the canyon wall and
returns to its origin (you). The result is
that you hear the echo (the reflected
sound wave) of your original yell.
Wave Properties: Refraction
When a wave enters a different medium
(more shallow region) at an angle, the
direction of waves changes. This change is
called refraction. The energy transferred
depends on the difference between the
mediums. If there is a significant difference,
almost all the energy will be reflected. If the
mediums are similar, most of the energy will
be transferred.
• Refraction causes objects to appear in a
different place than it actually is because
when light passes into a different medium
the light path bends.
Wave Properties: Interference
When two waves traveling in opposite
directions through the same medium
collide, the amplitude of the resulting
wave will be the sum of the two initial
waves. This is called interference and
there are of two types:
1. Constructive interference is when the
amplitudes of the initial waves are in the
same direction. The resulting wave will be
larger than the original waves.
2. Destructive interference is when the
amplitudes of the initial waves are
opposite. The amplitude of the
resulting wave will be zero.
Wave Properties: Polarizaton
• A light wave which is vibrating in more
than one plane is referred to as
unpolarized light. Polarized light waves
are light waves in which the vibrations
occur in a single plane. The process of
transforming unpolarized light into
polarized light is known as polarization.
Wave Properties: Resonance
• Resonance causes an object to move
back and forth or up and down.
For resonance to occur three things must be
present.
• A) An Object With a Natural Frequency.
• B) A Second Object that Can Oscillate at
the Same Frequency as the Natural
Frequency: Energy is transferred by a
wave from a vibrating object to a second
object.
• C) A Lack of Energy Loss: For an object to
resonate energy has to build up in the
object.
Electricity
Electricity generally refers to the flow of
electrons.
Types of Electricity
• Static Electricity - no motion of free
charges
• Current Electricity - motion of free
charges
– Direct Current (DC)
– Alternating Current (AC)
Electrical Circuits
A circuit is a loop of wire with its ends
connected to an energy source such as a
battery. One end of the wire is connected to
the positive terminal; the other end of the
wire is connected to the negative terminal. The
wire is connected in this way so a current can
flow through it.
Series Circuits
Resistors can be connected in series; that
is, the current flows through them one
after another.
Parallel Circuits
A parallel circuit is rather like two
or more series circuits connected to
the same energy source. For
example, here is a parallel circuit
connecting a battery and three
resistors.
• Series circuits have two
disadvantages when compared
with parallel circuits. The
first disadvantage is that, if
one component in a series
circuit fails, then all the
components in the circuit fail
because the circuit has been
broken. The second
disadvantage is that the more
components there are in a
series circuit, the greater the
circuit's resistance.
Parallel circuits have two advantages when
compared with series circuits.
• The first advantage of a parallel circuit is
that a failure of one component does not
lead to the failure of the other components.
This is because a parallel circuit consists of
more than one loop and has to fail in more
than one place before the other components
fail.
• The second advantage of parallel circuits is
that more components may be added in
parallel without the need for more voltage.
Ohm’s Law
• Ohm's Law deals with the relationship
between voltage and current in an ideal
conductor.
• Ohm's Law is given by:
•V = I R
R
V
I
Voltage
• Voltage (V) can be thought of as the
force pushing electric charges along a
conductor
Resistance
• Resistance (R) is a measure of how
difficult it is to push the charges
along.
Current
• Electric current (I) is the
movement of electric charge in a
conductor.