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# Waves:

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by

## Danielle Peters

on 11 May 2017

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#### Transcript of Waves:

Waves
A
wave
is a disturbance that travels through matter or space .
Waves
transmits (carries) energy
from one place to another

Types of Waves
Transverse Waves
Longitudinal Waves
Sound energy
travels in longitudinal waves
AKA compression waves
The particle motion is
parallel

to the path of the wave.
These waves
require a medium
in order to travel or be transmitted.
Sound needs matter (ie. solids, liquids, and gases) to travel

Behaviors of Waves
Absorption
When an object absorbs light energy and that energy is NOT used for a phase change (change in a state of matter), then the energy will be
transformed to heat energy
and the temperature of the object will increase.
Black absorbs
all wavelengths and
white tends to reflect
all wavelengths.

Waves:
Types, Properties and Behaviors

Properties
Electromagnetic Spectrum
The waves of the spectrum are all
transverse
(light) waves
All transverse waves travel at the
same speed

in a vacuum
You will need to be able to memorize:
The order of the waves in relation to frequency and wavelength
The order of the colors (visible light) in relation to frequency and wavelength

Waves can be described by the following physical properties:
speed
wavelength
frequency
amplitude
Speed
Wavelength
Frequency
Amplitude
Parts of a Transverse Wave
When waves travel they interact with different substances, and these interactions affect a wave's behavior.
Wave behaviors that we will focus on in Physical Science will include:
Absorption
Reflection
Diffraction
Refraction

Doppler Effect
Reflection
Diffraction
Refraction
Doppler Effect
Parts of a Longitudinal Wave
(light) travels in transverse waves
Particle motion is
perpendicular
to the path of the wave
These waves
do NOT require a medium
in order to travel or be transmitted.
Radiant Energy can travel through a vacuum
All waves are categorized and organized on the
Electromagnetic Spectrum

Crest:
high point of energy
Trough:

low point of energy
Amplitude:
height of the wave off the axis
Wavelength:

distance between two symmetrical points on a wave

Compression:
the area of the wave where the molecules are closer together.
Rarefaction:

the area of the wave in which the molecules are farther apart.
Wavelength:

distance between two symmetrical points on a wave

BIG IDEA!! The speed of a wave depends on the medium
Light Waves (Transverse):
Speed in a Vacuum = 299,792,458 m/s
Light travels
fastest in a vacuum
Sound Waves (Longitudinal):
Speed in a Vacuum = 0 m/s
Sound cannot travel in a vacuum because there is no matter (sound requires a medium)
Sound travels
fastest through solids
The frequency tells you how much energy a wave has –

the greater the frequency (f), the greater the energy
.
The frequency is the number of vibrations a wave produces each second.
Frequency is measured in Hertz (Hz)
1 Hertz = 1 vibration/second

Wavelength and Frequency have an inverse relationship:
High Frequency = Short Wavelength
Low Frequency = Long Wavelength

Light Waves (Transverse):
Greater Amplitude = Brighter = More Energy
Lower Amplitude = Dimmer = Less Energy

Sound Waves (Longitudinal):
Greater Amplitude = Louder = More Energy
Lower Amplitude = Softer= Less Energy

Reflection is the change in direction of a wave or when it bounced off a surface
Objects that do not emit (give off) their own light must reflect light in order to be seen
Ex: the moon, people, math textbook, etc.
We see things because light is being reflected off it

Color that we perceive is the result of that particular color being reflected back to your eyes while the other colors are absorbed
Law of Reflection:
The angle of incidence is equal to the angle of reflection.
In other words... the angle that light hits is the same measure as the light reflected

Refraction is the turning or bending of a wave (light or sound) when it passes from one medium into another of different density
.
A wave will
increase its speed
when it travels into a medium that is
less dense
A wave will
decrease its speed
when it travels into a medium that is
more dense

Diffraction
is the bending of waves (light or sound) around an object or through a slit.

Wave Interference
When 2 waves traveling through the same medium meet, they pass through each then continue traveling through the medium as before.
When waves meet, they undergo
superposition
, demonstrating
constructive
or
destructive
interference

Constructive Interference
Destructive Interference
Occurs when 2 waves have a displacement in the
same direction
(on the same side of the equilibrium)
The resultant wave will be
larger
because it is the sum of both waves
Occurs when 2 waves have a displacement in the
opposite direction
(on different sides of the equilibrium)
The resultant wave will be
smaller or zero
since it is the sum of a positive and a negative value
Doppler Effect
occurs when there is a change in the
frequency
and
wavelength

of a wave due to the source and the observer moving relative to each other
Doppler Effect with Light Waves
Doppler Effect with Sound Waves
When the source and observer are moving
towards
each other, the
wavelength is shorter
and
frequency is higher
As the source continues to get
closer
the sound will get
higher in pitch

When the source and observer are moving
away
each other, the
wavelength is longer
and
frequency is lower
As the source continues to get
farther
away the sound will get
lower in pitch

Misconception Alert!! Doppler Effect DOES NOT affect loudness

When the source and observer are moving
towards
each other, the
wavelength is shorter
and
frequency is higher
As the source continues to get
closer
the light will
appear blue

When the source and observer are moving
away
each other, the
wavelength is longer
and
frequency is lower
As the source continues to get
farther
away the light will
appear red

The BIG Connection:
Most of the observable universe appears red which we call "red shift." This means that the universe is continually expanding outward and helps support The Big Bang Theory.
Physical Properties of Objects Affect Light Waves
Types of Materials:
Opaque:
all light is either absorbed or reflected
Translucent:
some light is transmitted through and the rest is either absorbed or reflected
Transparent:
nearly all light is transmitted through but some may be reflected or absorbed

Physical Properties of Objects Affect Light Waves
Reflection of light off of
smooth surfaces
result in
clear
images

Reflection of light off of
rough surfaces
results in
fuzzy

images because light is reflected in all directions forming a
diffused
reflection
Reflection (cont.)
When a wave reflects off a surface the following happens:
the
direction
of the wave
changes
the
frequency
of the wave
remains unchanged
the
wavelength
of the wave
remains unchanged
the
amplitude
of the wave
changes (it is reduced)
the
speed
of the wave
remains unchanged

When a wave refracts upon entering another medium the following happens:
the
frequency
of the wave
remains unchanged
the
wavelength
of the wave
remains unchanged
the
amplitude
of the wave
changes
the
speed
of the wave
changes
Refraction (cont.)
Wave Interference
When two waves go through interference the following occurs:
the
frequency
of the wave
remains unchanged
the
wavelength
of the wave
remains unchanged
the
amplitude
of the wave
changes
the
speed
of the wave
remains unchanged

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