Light and Sound energy
Wave Definition
 A wave – is something that carries energy though
matter or space.
 Waves transfer energy
 Energy spreads out as waves move
 Most waves are caused by vibrating objects
 A medium – is the matter that waves move through
 Ex: water, air, space, even the earth can be a medium
Types of Waves
 Mechanical Waves – waves that require a medium to
travel through
 Examples: ocean waves and earthquakes
 Electromagnetic Waves- do not require a medium to
travel through and consists of moving electric and
magnetic fields traveling outward toward the speed of
light
 Examples: Light, magnetic force, radio waves
Transverse Waves
 Transverse waves- move particles up and down, perpendicular to
the wave motion
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Crest – top of the wave
Trough- bottom of the wave
Wavelength- distance from crest to crest or trough to trough
Amplitude- the distance from crest or trough to the starting
point of the wave
 Frequency – the number of wavelengths in a given time
 Period – the time is takes to complete a wave cycle
Examples of Transverse Waves
 Light, stringed instruments, radio waves, microwaves,
heat waves
 Red- longer slow wavelengths
Purple – short fast wavelengths
Longitudinal Waves
 Longitudinal Waves- particles move parallel to the
direction of the wave
 Compression- “squished” part of the wave (compressed)
 Rarefaction – stretched part of the wave
 Wavelength – distance from compression to
compression or rarefaction to rarefaction
Examples of Longitudinal Waves
 Sound, some earthquakes, deep water waves
Surface Waves
 Surface waves- are water waves that are both transverse
and longitudinal waves
 Surface waves cause objects to move in a circular
motion on the surface
Formulas
 Wave speed = wavelength X frequency
 Wavelength = speed
frequency
 Frequency = speed
wavelength
Ways Waves Interact
 Reflection
 Refraction
 Diffraction
 Interference
 Constructive
 Destructive
Standing Waves
Reflection
 When an object or
wave hits a surface
through which it
cannot pass, it
bounces back.
 Angle of incidence
 Angle of reflection
Examples of reflection
 Mirror
 Echo
 Ball against a wall
Refraction is when a wave moves
from one medium into another
medium at an angle, it changes
speed as it enters the second
medium which causes it to bend.
The bending of waves due to a
change in speed is called
refraction.
Refraction
 Though all waves
change speed when
they enter a new
medium. Bending
occurs when one side
of the wave enters the
new medium before
the other side
Diffraction
 When a wave passes a barrier or moves through a hole
in a barrier it bends and spreads out.
Interference
 Constructive interference occurs whenever two waves
combine to make a wave with a larger amplitude.
 Destructive interference when the amplitudes of two
waves combine producing a smaller amplitude.
Standing waves:
 If the incoming wave and the reflected wave combine
at the right places the combined wave appears to be
standing still.
 It appears to be standing in one place, even though it is
two waves interfering as they pass through each other.
Nodes and Antinodes
 node: at certain points,
destructive interference
causes the two waves to
combine and produce an
amplitude of zero.
 Antinode are the points
of maximum energy.
The crests and troughs of
a standing wave.
Resonance
 Most objects have a natural frequency of vibration.
Resonance occurs when vibrations traveling through
an object match the object’s natural frequency.
 An object that is vibrating at its natural frequency
absorbs energy from the objects that vibrate at the
same frequency. Occurs in music.