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Chapter Introduction
Lesson 1
The Nature of
Energy
Lesson 2
Waves and Sound
Lesson 3
Properties of Light
Lesson 4
Electromagnetic
Waves
Lesson 5
Heat
Lesson 6
Electricity
Chapter Wrap-Up
What are the different
forms of energy?
The Nature of Energy
Essential Question
• What forms can energy take and
how do they compare?
The Nature of Energy
Energy
Kinetic energy
Potential
energy
Chemical
potential
energy
Elastic potential
energy
Gravitational
potential energy
Law of
conservation of
energy
What is energy?
• Everywhere around you changes are
occurring.
– Ex. Electricity into light and heat energy
Plants turn sunlight into food
You shifting in your seat.
• Every change that occurs – whether it
is large or small – involves energy.
What is energy? (cont.)
• Energy is the ability to cause change.
• Energy can cause changes in the motions of
objects.
• Anything that causes change, must have
energy.
– Ex. You use energy when you travel to school,
whether you walk, ride in a car, or take the bus.
• Energy is measured in units called joules (J).
What is energy? (cont.)
• Energy comes in many forms.
Forms of Energy
Form
Nuclear
Chemical
Electrical
Light
Mechanical
Sound
Thermal
Example of Source
the Sun, radioactive material
food
a generator, a battery
the Sun, an electric lamp
moving parts in a machine
vibrations of a stereo speaker
hot water in a radiator
• All forms of energy have one thing in common:
they have the ability to cause change.
What are kinetic and potential
energy?
• You know that there are many forms of
energy. But all forms of energy can be
classified as potential or kinetic energy.
• Kinetic energy is the energy of motion.
What are kinetic and potential
energy? (cont.)
• All moving objects have kinetic energy.
• The faster an object moves, the more
kinetic energy it has.
• If two objects move at the same speed,
the object with more mass has more
kinetic energy.
What are kinetic and potential
energy? (cont.)
• The kinetic energy (KE) of an object depends
on its speed and its mass. The vertical bars
show the kinetic energy of each vehicle.
What are kinetic and potential
energy? (cont.)
• There are different forms of kinetic
energy.
– Ex. Electricity is related to kinetic energy of
electrons.
Sound is the kinetic energy of particles
as they move in waves.
What are kinetic and potential
energy? (cont.)
• Energy doesn’t have to involve motion.
Even motionless objects can have
energy.
• Potential energy is the energy stored in
an object or a material.
– Ex. A rock at the top of a hill. Has the
potential to cause change by rolling down
the hill.
What are kinetic and potential
energy? (cont.)
• Objects can have a combination of
potential and kinetic energy –
mechanical energy.
– Ex. Roller coasters
At the top of the hill – high potential
energy and low kinetic energy.
Coming down the hill – potential energy
decreases and kinetic energy
increases.
What are the forms of potential
energy?
• Chemical potential energy is energy stored in
the chemical bonds between atoms.
– Ex. Food, gasoline
What are the forms of potential
energy? (cont.)
• Elastic potential energy is the energy
stored in something that can stretch or
compress.
– Ex. Spring, rubber band when stretched or
compressed
What are the forms of potential
energy? (cont.)
• Gravitational potential energy is the
energy stored in objects due to their
position above Earth’s surface.
• The GPE of an object depends on the
object’s mass and height above the
ground.
– Ex. Dropping a bowling ball from 1m causes
a greater change than dropping a tennis ball
from 1m.
How does energy change?
• Energy can change from a potential to a
kinetic form
• In the world around you, energy is
transforming continually between one
form and another.
How does energy change? (cont.)
– Ex. A microwave oven changes electric
energy into radiant energy.
How does energy change? (cont.)
• Energy enables things to move.
• Machines and living things need chemical
energy – in the form of fuel or food – to get
from one place to another.
– Ex. Walking or jogging = Muscles change
chemical energy from the food you ate into
mechanical energy.
Moving your car = engine changes chemical
energy from fuel into heat. The heat
powers the engine in the form of
mechanical energy.
How does energy change? (cont.)
• Energy is also required in manufacturing.
– Ex. Clothes, paper, computers, microwaves
• Factory machines use electrical or
chemical energy to run.
• They generate thermal energy as a
byproduct of their mechanical
movement.
Where does energy go?
• Law of conservation of energy is a
physical law that states that energy may
change form but it cannot be created or
destroyed.
– Ex. Applying the brakes of your bicycle. A
moving bicycle has mechanical energy.
• When you apply the brakes that energy is not
lost or destroyed, it is transformed into thermal
energy from the friction between the brake pad
and the wheel.
Where does energy go? (cont.)
• In the example before, the mechanical
energy to move the bike came from
chemical energy in your muscles.
• The chemical energy in your muscles
came from the food you ate.
• The chemical energy in the food ate
came from the Sun.
– Where did the Sun’s energy come from?
Where does energy go? (cont.)
• The Sun’s energy is generated
through a process called nuclear
fusion.
• Nuclear fusion occurs when the Sun
and other stars convert a tiny amount
of mass into an enormous amount of
energy.
Where does energy go? (cont.)
• Nuclear power is generated on Earth
by nuclear power plants.
• These power plants split atoms in a
process called nuclear fission.
Where does energy go? (cont.)
• A tremendous amount of thermal energy is
released during nuclear fission.
When is heat “lost”?
• Many chemical reactions will not occur
without heat.
• Sometimes this heat is an unwanted
waste product.
– Ex. Heat generated by friction causes many
machines, like your car, to break. Friction
and heat wear down machine parts. If this
heat, cannot be released, your car will stop
working.
Where would a book have the
most potential energy?
A. on the floor
B. on the top shelf of a bookcase
C. on the middle shelf of a bookcase
D. on the lowest shelf on a bookcase
Which type of energy increases
when you compress a spring?
A. elastic potential energy
B. kinetic energy
C. chemical potential energy
D. gravitational potential energy
Which term refers to energy due
to motion?
A. kinetic energy
B. potential energy
C. sound energy
D. stored energy
Waves and Sound
Essential Question
• How to waves cause sound?
Waves and Sound
Wave
Frequency
Wavelength
Sound wave
Amplitude
Reflection
What are waves?
• Wave is a disturbance that transfers
energy from one point to another.
• Electromagnetic waves can travel
through empty space and matter.
– Ex. Light waves
What are waves? (cont.)
• Mechanical waves must travel through a
medium – a substance – in order to
transfer energy
– Ex. Sound waves
• A medium can be a solid, liquid or gas.
• The movement of particles by a wave is
called a vibration.
What are waves? (cont.)
• Waves are classified by the type of vibration
they cause in a medium.
– Transverse waves – when a transverse wave
travels through a medium, matter moves up and
down as the wave travels through it.
• Ex. Water waves
What are waves? (cont.)
– Compressional wave– when a
compressional wave travels, matter moves
back and forth as the wave travels through it.
• Similar to a spring or a slinky.
• Ex. Sound waves
What are waves? (cont.)
• All waves travel and transfer energy from
one point to another, with little or no
displacement of the particles of the
medium.
• After the wave has passed, the particles
end up in about the same position they
started in.
How can you measure waves?
• Wavelength is the distance between two
waves’ crests or two waves’ troughs.
• OR The distance between two waves’
compressions or rarefactions.
How can you measure waves?
• Amplitude is the height of a wave from
its trough or crest to its midpoint.
How can you measure waves?
• The wave with the larger amplitude
carries more energy and makes the ball
bounce higher.
How can you measure waves? (cont.)
• Frequency is a measure of how many
wave crests or troughs pass a given
point in one unit of time.
– High-frequency waves have shorter
wavelengths and transfer greater energy.
How can you measure waves? (cont.)
• The period of a wave is the amount of
time it takes for a wave to complete one
full cycle.
• Frequency is measured in hertz (Hz), the
number of waves per second.
– Ex. 5 waves in 20seconds.
5 ÷ 20 = 0.25 Hz.
How can you measure waves? (cont.)
• The distance a wave travels per second
determines its speed.
– Ex. A boat passes within 65m of a buoy.
The waves from the boat take 5seconds to
reach the buoy.
Wave speed = 65 ÷ 5 = 13m/s
• The speed of a wave depends on its
medium, not its frequency!
– Ex. A high-frequency wave can travel slowly
How does sound travel?
• Sound wave is a
compressional wave produced
by vibrations in matter.
• Molecules in the medium
moved back and forth, pushing
nearby molecules.
• Because sound waves depend
on the compression of matter,
they need a medium to travel
through.
How does sound travel? (cont.)
• In sound waves, the
distance between the
particles affects
speed.
• Sound waves move
fastest through solids,
slower through liquids
and slowest through
gases.
Medium
Air
Speed
(in m/s)
334
Freshwater
1,461
Seawater
1,490
Silver
2,610
Glass
5,000
How does sound travel? (cont.)
• When you look in a mirror, light waves
bounce off the mirror into your eyes and
enable you to see your image.
• Sound waves also reflect off of objects.
• Reflection is the bouncing of a wave off
an object, changing the direction of
travel.
– Ex. An echo and sonar
How does sound travel? (cont.)
• The material a sound wave strikes
affects how the sound wave moves.
• Hard surfaces reflect sound waves,
soft surfaces absorb sound waves.
– Absorption is the transfer of energy
when a wave disappears into a
surface.
• Ex. Ceiling tiles, insulation
• A material that absorbs sound
waves well does not reflect sound
waves.
What are properties of sound?
• The pitch or the highness
or lowness of a sound,
depends on the frequency
of the sound waves.
– High pitched sounds have a
high frequency
– Low pitched sounds have a
low frequency
• Most humans can hear
sound waves in the range
of about 20Hz to about
20,000Hz.
What are properties of sound? (cont)
• A sound’s pitch seems to change if its
source or listener is moving.
– This is called the Doppler effect.
What are properties of sound? (cont)
• The difference in the loudness of a
sound is called volume.
• The amount of energy, or intensity
(amplitude), of the sound wave
determines the volume of a sound.
– The larger the amplitude, the louder the
sound.
What are properties of sound? (cont)
• The volume of a sound is measured in units
called decibels (dB)
– Regular speech have a volume of about 60dB.
– Sounds greater than 90dB can damage people’s
hearing.
What are properties of sound? (cont)
• The motion of two or more waves
passing through the same medium at the
same time is called interference.
– Ex. Two sets of speakers playing the same
song in the same room.
What are properties of sound? (cont)
• Interference can be positive for negative.
– If the crests or troughs of the waves meet,
they would combine and the combined
sound would be louder – constructive
interference.
– If the crest of one wave meets the trough of
another wave, combined amplitude is lower
than the sound made by one source alone –
destructive interference.
How do we hear music?
• Sound waves pass through your ear
canal to your eardrum causing your
eardrum to vibrate.
• The vibrations stimulate nerve cells
located deep inside the ear.
• These vibrations are then converted to
nerve impulses that your brain
recognizes and identifies as different
sounds.
How do we hear music? (cont.)
How do we hear music? (cont.)
• Music is a combination of sounds that a
listener finds pleasing.
• Noise is a combination of sounds that a
listener finds unpleasant.
Which occurs when waves that
overlap combine to form a new
wave?
A. diffraction
B. interference
C. reflection
D. refraction
To measure the wavelength
of a transverse wave, you can
measure the distance from one
crest to which of these?
A. the next crest
B. the next trough
C. the next compression
D. the next rarefaction
Which refers to the number of
wavelengths that pass by a point
each second?
A. amplitude
B. compression
C. frequency
D. wavelength
Properties of Light
Essential Question
• How does light move and
change?
Properties of Light
Transparent
Translucent
Opaque
Law of
reflection
Refraction
How does light travel?
• Light is a form of energy that travels in
waves.
• Light waves spread out as they move
away from a source.
• Light travels in straight lines called rays.
How does light travel? (cont.)
• Light waves can carry energy through
space and some matter.
• Light travels through space at the fastest
speed matter and energy can possibly
reach: about 300,000 km/s
• A light ray will not change direction
unless it travels through a different
medium or is disturbed in some way.
How does light travel? (cont.)
• Transparent allowing light to pass
through with almost no distortion.
• Objects look clear and crisp behind
transparent material.
• Ex. Lens in eyeglasses
How does light travel? (cont.)
• Translucent allowing some light to travel
through and blocking some light or
bouncing it in a different direction.
– Objects appear blurred behind translucent
material.
– Ex. Stained glass, lampshades
How does light travel? (cont.)
• Opaque not allowing light to pass
through.
– Object is not seen behind opaque material.
– Casts a shadow when it is in front of a light
source.
– Ex. Books, walls, glass of milk
How does light act with mirrors?
• Law of reflection is
a physical law that
states that the angle
between an incoming
light ray and a
surface is equal to
the angle between
the reflected light ray
and the same
surface.
How does light act with mirrors?
(cont.)
• Any surface that reflects light and forms
images is a mirror.
– Plane mirror – has a flat surface. The
images appear to be exact copies, though
they are reversed.
How does light act with mirrors?
(cont.)
– Concave mirror
• has a surface that curves inward.
• Light rays are reflected and meet at a point
located in front of the mirror dependent on the
curve of the mirror.
• An object placed close to a concave mirror will
produce a large image that right-side-up.
• As you move the object away, the image will
become blurry, smaller and eventually appear
upside down.
How does light act with mirrors?
(cont.)
– Concave mirror (cont.)
• Are used to gather light inside of telescopes.
• Used in make-up or shaving mirrors – to make
the face appear larger and in more detail.
How does light act with mirrors?
(cont.)
– Convex mirror
• has a surface that curves outward.
• Light rays are reflected from the surface and
spread out, producing a wide-angle view.
• Always produces an image that is right-side-up
and much smaller than the object.
How does light act with mirrors?
(cont.)
– Convex mirror (cont.)
• Useful for security in stores and providing a better
view for drivers of vehicles.
What is refraction?
• Light always travels through empty
space at the same speed – 300,000km/s
• However, light travels slower when it
moves through a medium, such as air,
glass or water.
What is refraction? (cont.)
• Refraction is the
change in direction of
a wave because of a
change in the medium
it is traveling through.
• When light moves into
a medium where its
speed decreases, the
ray bends toward the
normal.
What is refraction? (cont.)
• When light moves into
a medium where its
speed increases, the
ray bends away from
the normal.
• The larger the change
in speed of the light
wave is, the larger the
change in direction is.
What is refraction? (cont.)
• A lens is a transparent object with at
least one curved side that causes light to
change direction.
• Light refracts as it passes through a lens.
• The greater the curve of the lens, the
more the light refracts.
What is refraction? (cont.)
• A lens that is thicker in the middle than
at the edges is a convex lens.
• A lens that is thicker at the edges than
in the middle is a concave lens.
What is refraction? (cont.)
• A convex lens refracts light
inward and it converges.
• If the object is located
between the lens and its
focal point, the image is
right-side-up and larger
than the object.
• If the object is located
beyond the focal point, the
image is upside down and
smaller than the object.
What is refraction? (cont.)
• A concave lens refracts light rays apart. It
diverges.
• A concave lens is thinner in the middle than it is
at the edges.
• The image is always right-side-up and smaller
than the actual object.
How is light refracted by
telescopes and cameras?
• Much of what is known about the universe has
come from images and other information
gathered by telescopes.
• A telescope is a device that collects light and
magnifies images to make distant objects appear
closer.
• Telescopes use mirrors and lenses to gather
light.
How is light refracted by
telescopes and cameras?
• Refracting telescopes use two convex lenses
to form an image of a distant object.
• Light passes through
an objective lens
that forms an image.
• The image is then
magnified by a lens
in the eyepiece.
How is light refracted by
telescopes and cameras?
• Reflecting telescopes have a concave mirror
instead of a concave objective lens to gather
light.
• The large concave
mirror focuses light
onto a secondary
mirror that directs it
to the eyepiece,
which magnifies the
image.
How is light refracted by
telescopes and cameras?
• Cameras have a lens or a system of lenses that
converge light rays toward a sensor.
• On some cameras, you can zoom, or make the
image larger, by moving the lenses, which
changes the focal length of the lens and lets you
photograph distant and close objects.
How can we correct vision?
• The internal shape of your eyes plays a role in
how they function.
• If your eye shape is even slightly off, your vision
will be impaired.
How can we correct vision? (cont.)
• A nearsighted person has at least one eye that
is longer than normal from front to back.
• This causes light rays from distant objects to be
focused in front of the retina. As a result
nearby objects are clear but distant objects look
blurry.
How can we correct vision? (cont.)
• Concave lenses
spread the light
rays before they
reach the eye so
the rays travel a
longer distance
and focus at the
correct spot.
How can we correct vision? (cont.)
• A farsighted person has at least one eye that
is shorter than normal from front to back.
• This causes light rays from nearby objects to be
focused in behind the retina. As a result,
distant objects are clear but nearby objects look
blurry.
How can we correct vision? (cont.)
• Convex lenses
bend the light rays
closer together
before they reach
the eye so the rays
are focused
properly on the
retina.
A material that allows most of the
light that strikes it to pass
through and form a blurry image
is called what?
A. luminous
B. opaque
C. transparent
D. translucent
Which is a mirror that curves
inward?
A. concave mirror
B. convex mirror
C. plane mirror
D. virtual mirror
Which term refers to a lens that is
thicker in the middle than at the
edges?
A. concave lens
B. convex lens
C. prism
D. rod
Electromagnetic
Waves
Essential Question
• How do the types of
electromagnetic waves compare?