Transcript Physical Science EOCT Review Domain IV Waves, Electricity and

Physical Science EOCT Review
Domain IV
Waves, Electricity and Magnetism
Parts of a Wave
Mechanical (Longitudinal) Waves
Examples are sound waves and slinkys
Electromagnetic Waves
(Transverse)
• Electromagnetic waves are transverse
waves
which have both an electric and and
magnetic effect.
• The energy of the photons is directly
proportional to the frequency.
Light
• Light is a form of electromagnetic radiation (EM)
• EM spectrum shows the forms of radiation in
order of increasing frequency (and energy) and
decreasing wavelength
Color of Light
• We see different colors depending on the
•
frequency of light emitted or reflected
This is the reason blue flames are hotter than
yellow. Blue has a higher frequency so more
energy.
Sample Question
• How are the frequency and wavelength
related to the energy carried by waves?
– Answer: Higher frequency waves have more
energy while longer wavelength waves have
less energy. Frequency and energy are
directly related while wavelength and energy
are inversely related. Radio waves (long
wavelength) have less energy than gamma
waves (high frequency).
Sample Question
• How are frequency and wavelength
related?
– Answer: Frequency and wavelength are
inversely related. High frequency waves have
short wavelengths.
Electromagnetic Wave (EM) versus
Mechanical Wave
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•
•
EM WAVE
does not require
matter to transfer
energy
CAN travel through a
vacuum
example: light
MECHANICAL WAVE
• does require matter
to transfer energy
• CANNOT travel
through a vacuum
• example: sound
Sample Question
• Make a Venn Diagram to Compare
electromagnetic and mechanical waves.
– Sample Answer: Electromagnetic waves (light)
do not require matter to transfer energy while
mechanical waves (sound) require matter to
transfer energy. In other words, EM waves will
travel in a vacuum while mechanical waves
will not.
Reflection of Light
• When light strikes a
•
•
boundary, it reflects.
The angle at which the
wave approaches a flat
reflecting surface is equal
to the angle at which the
wave leaves the surface
(like a bounce pass of a
basketball).
Reflection results in
image formation.
Diffraction
We say that the wave bends around
the barrier, or that it changes
directions. Where the wave was
traveling in a straight line before
passing the barrier, it is now 'bent' or it
changed direction after passing the
barrier.
DIFFRACTION of a wave is the
bending or redirection of the travel of
the wave when it passes a barrier
without changing the medium in which
the wave is traveling.
Refraction of Light
• Light waves travel
faster in air than in
water and slower in
glass than water.
• More dense =
slower light
• When light enters a
different medium,
speed changes and
it bends.
• Bending of light due
to change in speed
= REFRACTION
Sample Question
A.
B.
C.
D.
Reflection only
Refraction only
Both Reflection and Refraction
Neither Reflection or Refraction
The correct answer is “C” because
some
The light will be reflected some
will be absorbed
And therefore refracted
Sound and mediums
Remember that Density is the key to how
Fast it travels!
Sound travels fastest
through solids. This is
because molecules in a solid
medium are much closer
together than those in a
liquid or gas, allowing
sound waves to travel more
quickly through it. In fact,
sound waves travel over 17
times faster through steel
than through air. The exact
speed of sound in steel is
5,960 meters per second
(13,332 mph)! But, this is
only for the majority of
solids. The speed of sound
in all solids are not faster
than in all liquids.
Wave Interference
• the phenomenon
•
•
which occurs when
two waves meet while
traveling along the
same medium
constructive =
waves add to produce
a larger wave
destructive = waves
cancel to produce a
smaller wave
CONSTRUCTIVE
DESTRUCTIVE
The Doppler Effect
• observed whenever
•
•
•
the source of waves
is moving with
respect to an
observer
an apparent change
in frequency occurs
toward = higher
frequency
away = lower
frequency
Electricity
• Electrons carry a negative charge.
• Lost electrons = positive charge
• Gained electrons = negative charge
• REMEMBER:
– Like charges repel
– Opposites attract
Static Electricity
•
•
•
•
3 causes:
Friction
Conduction
Induction
If you charge a balloon by rubbing it on your hair, it picks up extra electrons
and has a negative charge. Holding it near a neutral object will make the
charges in that object move. If it is a conductor, many electrons move easily to
the other side, as far from the balloon as possible. If it is an insulator, the
electrons in the atoms and molecules can only move very slightly to one side,
away from the balloon. In either case, there are more positive charges closer
to the negative balloon. Opposites attract. The balloon sticks.
Electrical Circuits
SERIES
• Current flows in a
closed circuit
• Two types of circuits:
– Series (single path)
– Parallel (many paths)
PARALLEL
2 types of electrical currents
Direct current DC
• Means to move
continuously in the
same direction
• Car Batteries is an
example
Ohm’s Law
Alternating Current
AC
• have electrons that
can change direction
• a gasoline-driven
generator is an
example
Relates current, voltage and resistance
Sample Question
The correct answer is “B”
Electromagnet
• One can make an electromagnet with a nail, battery, and
•
wire
When current flows through the coiled wire, the nail
becomes magnetized. The more wraps-the greater the
energy.
Electric Generators
Faraday discovered that if an electric conductor,
like a copper wire, is moved through a magnetic
field, electric current will flow (be induced) in
the conductor. So the mechanical energy of the
moving wire is converted into the electric energy
of the current that flows in the wire.
This is called electromagnetic induction
Sample Question
The correct answer is “A”
Sample Question
•
When a loop of wire is turned in
a magnetic field, electrical
charges move through the
wire, creating an electrical
current. This is the basis for an
electric generator, so answer D
is correct.
Figure Reference
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Distance versus Time Graph figures: source unknown
Forces figure: retrieved from
http://www.glenbrook.k12.il.us/gbssci/phys/CLass/newtlaws/u2l2
c1.gif
Determining the Net Force figure: retrieved from
http://www.glenbrook.k12.il.us/gbssci/phys/CLass/newtlaws/u2l2
d11.gif
Newton’s Laws, Gravity, Work, Types of Mechanical Energy,
Conservation of Energy, Light, Interference, and Doppler Effect
figures: retrieved from http://www.physicsclassroom.com
Electrical Circuits figures: retrieved from
http://www.autoshop101.com/trainmodules/elec_circuits/circ101.
html
Electromagnet figure: source unknown