Download Waves - Northside Middle School

Waves
The Nature of Waves
• A wave is a disturbance
or vibration that
transfers energy from
one place to another.
• Waves transfer energy,
not matter. The water
waves below are
carrying energy but are
not moving. Waves can
only exist if they have
energy to carry.
For sound:
When two objects hit each
other or rub against each
other, they begin to vibrate
quickly, faster than the eye
can see. This vibration
shakes the air, and the
vibration in the air moves
outward in the form of a
wave.
The vibrations eventually
hit your ear, and you hear
the sound.
Light
Light is a type of electromagnetic wave.
Light has both an electric field and a magnetic
field. It is because of this reason that light is
also referred to as electromagnetic energy.
Light travels as the electric fields and magnetic
fields go up and down.
There are two types of waves:
Compression waves are waves which require a medium. A medium is a form of
matter through which the wave travels (such as water, air, glass, etc.)
In a compression wave the matter in the wave moves back
and forth.
Transverse waves, such as light, x-rays, and other forms of radiation do not
require a medium. They can travel without going through air, water, or any solid
object.
In a transverse wave the matter in the wave moves up and
down.
Examples of waves:
Waves can be both compressional and
transverse, like seismic waves.
A seismic wave is an energy wave which vibrates through the earth’s crust
as the crust bends or breaks. Seismic waves exist as both transverse and
compressional waves. Some travel through the earth and some travel
across the earth’s surface.
What are the parts of a wave?
Transverse wave
The crest is the highest
point on a transverse
wave. The trough is the
lowest point on a
transverse wave.
The wavelength is the
distance from one point
on the wave to the next
corresponding point.
Compressional
wave
On a compressional wave
the area squeezed
together is called the
compression. The areas
spread out are called the
rarefaction.
The wavelength is the
distance from the center of
one compression to the
center of the next
compression.
What is wave frequency?
Frequency is the number of waves that pass through a
point in one second. The smaller the wavelength, the
more times it will pass through a point in one second.
The larger the wavelength, the fewer times it will pass
through a point in one second.
Different Frequencies in a Pendulum Wave
The amplitude of a transverse wave is determined by
the height of the crest.
The amplitude of a compression wave is determined
by the closeness of the compression.
The amplitude of a wave is directly related to the energy of a
wave, the larger the amplitude, the more energy in the wave.
High Energy
The Behavior of Waves
Waves can reflect: When a wave bounces off an
object and changes direction – this is reflection.
Waves can refract:
Refraction is the bending of a
wave as it passes from one
medium to another. A wave
travels at different speeds in
different things. When a wave
traveling a certain speed
moves into another medium
(like from air to water), it will
either increase in speed or
decrease in speed, which
changes the way we see an
object.
Waves can diffract:
Diffraction occurs when an object causes a
wave to change direction and bend around it.
Diffraction also occurs when waves (especially sound)
pass through a small opening. They diffract and spread
out as they pass through the hole.
When waves run into each other, it is called
interference.
You can think of it as adding and subtracting waves! If they are
moving the same way, you add them. If they are moving in the
opposite directions, you subtract them.