Download Why are both electromagnetic and mechanical waves needed to

Why are both electromagnetic and mechanical waves needed to make movies?
S8P4a. Identify the characteristics of electromagnetic and mechanical waves.
Name: __________________
Date:___________________
MEDIUM: any substance
through which waves travel.
A medium can be a solid,
liquid, gas or plasma. Empty
space (vacuum) is not a
medium!
Waves
transfer energy but do not carry medium with them
Electromagnetic (EM)
Mechanical
Waves that do not need a medium to travel; can travel through
empty space. All the waves on the electromagnetic spectrum
(below) can travel through empty space.
Waves that need a medium to travel. Cannot travel through
empty space.
Longitudinal
a type of mechanical wave
longitudinal waves move back and
forth parallel to movement of
energy.
Sound and seismic are longitudinal,
mechanical wave
Transverse
Surface
surface waves are mechanical
combination of longitudinal
and transverse waves
circular motion at the surface
water was are an example
are electromagnetic waves
transverse waves move up and
down perpendicular to movement of
energy
light, microwaves, UV light, Xrays
etc. are all transverse waves
S8P4f. Diagram the parts of the wave and explain how the parts are affected by changes in amplitude and pitch.
Diagram the parts of a wave including their properties for both longitudinal and transversal waves.
Longitudinal
Transverse
S8P4f. Diagram the parts of the wave and explain how the parts are affected by changes in amplitude and pitch.
What are the three properties of a wave that can be measured?
1. Amplitude
The distance a wave moves away from the rest position. Amplitude
is altitude or height. Higher amplitude = higher energy.
Loudness/volume
increasing the amplitude
increases the volume.
2. Wavelength
the distance between 2 corresponding points on a wave. For example, the distance between 2 crests
or two troughs. When the wavelength goes up the frequency goes down. Shorter wavelength =
higher frequency = higher energy.
3. Frequency
The number of waves that pass a given point in a set amount of time.
To frequency, count the number of crests or troughs you see in a
given time period. Frequency is measured in Hertz (Hz). When the
frequency goes up the wavelength must go down. Higher frequency =
higher energy!
Pitch: is how high or low the
sound is. This is not the
same as volume. Think
music…higher like a violin or
lower like a bass.
The higher the frequency the
higher the pitch.
Wave Behaviors
Reflection
Reflection is the bouncing
back of a wave. You see
what is reflected.
Law of Reflection:
the angle of incidence is
equal to the angle of
reflection
Diffraction
Diffraction is the
bending of a wave
around a barrier or
through an
opening.
Diffraction
depends on the
size of the barrier
and the
wavelength.
Refraction
Refraction is the
bending of a wave as
it moves from one
medium to another.
This is why rainbows
occur and why a
straw looks bent in a
glass of water.
Refraction depends
on the wavelength of
the wave.
Interference
Constructive
Destructive
In constructive interference (a) the crests or troughs overlap
and create a larger wave.
In destructive interference (b) a crest may overlap a trough
and they would cancel out.
SOUND
What is sound? a mechanical wave that is longitudinal created by the vibrations of particles
How do you detect sound?
Outer Ear: collects sound and funnels to eardrum
Middle Ear : Ear drum vibrates and 3 bones
amplify sound
Inner Ear: Cochlea transfers sound into nerve impulses to the brain
Speed of Sound: 345m/s in air at room temperature. The speed of sound depends on 2 things: 1)temperaturesound travels fastest through objects at warmer temperature because the particles are moving more quickly; and
2) the medium-sound travels fastest through solids then liquids then gases. It does so because the particles in a
solid are closer together.
Pitch and Frequency: the higher the frequency the higher the pitch
Doppler Effect: The Doppler Effect is the apparent change in the frequency of a sound caused by the motion of either the
listener or the source of the sound.
Loudness and Amplitude: Increasing the amplitude of a wave increases the volume
INTERACTIONS OF SOUND WAVES
Reflection (Echo): An echo is a reflected sound wave
Echolocation: The use of echoes to locate objects. Bats and dolphins use echolocation.
Interference: causes sonic boom as waves overlap and create a high density compression
Sonic boom: the sound that is created when an object moves faster than the speed of sound. Occurs because the
object moves through a wave that has constructively interfered.
Resonance: when one object’s vibrations causes another to vibrate at the same frequency. This is why opera
singers can crack glass
LIGHT
Speed of Light: 900,000 faster than the speed of light. 300,000 km/s or 3,000,000,000 m/s which is why you see the lightening
before hearing the thunder.
Electromagnetic Spectrum: all the electromagnetic waves are listed on the electromagnetic spectrum (see page 1). The
EM Spectrum is arranged according to wavelength/frequency. Radio waves (left) have the longest wavelength and lowest frequency
and are the least harmful because they have the lowest energy. Gamma Rays have the shortest wavelength/highest frequency and
are the most dangerous. Visible light is towards the middle of the EM spectrum and includes the colors of the rainbow (ROYGBIV).
The colors are arranged from longest wavelength (red) to shortest (violet).
Absorption:
when the medium absorbs the light ; causes the beam of light to dim
Scattering: when light bounces of particles in the air; explains why the sky is blue
Light and Color:
Transparent-most of the light is transmitted or passes through (plastic wrap)
Translucent-some of the light is transmitted (wax paper)
Opaque-no light is transmitted (foil)
How is color determined?
Transparent/Translucent- color is determined by the amount of light that passes through.
A 2 liter of ginger ale is green
is transmitted.
Opaque-color is determined by the color(s) that are reflected.
For instance, a red object reflects red light only, a purple object
reflects red and blue (colors that make purple); white objects reflect all 7 colors and black objects absorb all the color.