Transcript Waves

Thursday, March 12, 2015
• Learning Target: I will understand how
waves move and the different types of
waves.
• Warm up
• Notes on Waves, properties & behaviors
• Notebook pages 176-184 – due Tuesday
• Waves vocab- due Tuesday
Warm up – March 12
• What is a wave?
Wave vocab words
• Wave
• Mechanical wave
• Electromagnetic
waves
• Transverse waves
• Compressional waves
• Amplitude
• Wavelength
• Frequency
• Wave Speed
•
•
•
•
•
•
•
•
Crest
Trough
Compression
Rarefaction
Reflection
Refraction
Diffraction
Constructive
interference
• Destructive interference
Waves
Definition: A wave is a
rhythmic disturbance that
carries energy through matter
or space.
Mechanical Waves
• Mechanical waves can only travel through
matter.
– The matter through which a mechanical
wave travels is called a medium.
• A mechanical wave travels as energy is
transferred from particle to particle in a
medium.
– Example: water waves, sound waves
Electromagnetic Waves
• Electromagnetic waves do not require matter
to carry energy.
– Electromagnetic waves can travel through a
medium, but they can also travel through
outer space or through a vacuum where no
matter exists.
– Example: Radio waves,
Microwaves, infrared,
Visible light, UV, x-rays
and gamma rays
Transverse Waves
• In a transverse wave, the wave energy causes
the matter in the medium to move up and
down or back and forth at right angles to the
direction the wave travels.
Compressional Wave
• In a compressional
wave, matter in the
medium moves
forward and
backward in the
same direction that
the wave travels.
• Compressional
waves are also
known as
longitudinal waves.
• Mechanical Waves can be either transverse or
compressional waves.
• Electromagnetic Waves can only be transverse
waves.
Wave
Properties
Crest and Trough
• The high points of transverse waves are
called crests,
• The low points are called troughs.
Wavelength
• For a transverse wave, wavelength is the
distance from the top of one crest to the
top of the next crest, or from the bottom
of one trough to the bottom of the next
trough.
Amplitude
• The amplitude
of a transverse
wave is onehalf the
distance
between a crest
and a trough.
Amplitude and Energy
A wave’s amplitude is related to the energy
that the wave carries.
The greater the
amplitude, the
greater the
energy carried
by that wave.
Frequency
• The frequency
of a wave is the
number of
wavelengths
that pass a
given point in 1
second.
The unit of frequency is the number of
wavelengths per second, or hertz (Hz).
Frequency & Wavelength
• Longer
wavelengths
result in
smaller
frequencies.
Shorter
wavelengths
result in larger
frequencies.
Wave Speed
• Wave speed = frequency x wavelength
(m/s)
(Hz)
(m)
Equation : v = f λ
• Find the speed of a wave with a
wavelength of 5 m and a frequency of 68
Hz.
Compression
• The point in a
compressional
wave where
the matter is
squeezed
together.
Rarefaction
• The point in a
compressional wave
where the matter is far
apart.
Wavelength
• For a compressional wave, the
wavelength is the distance between the
center of one compression and the
center of the next compression.
Wave Behavior
Reflection
• Reflection occurs when a wave strikes an
object or surface and bounces off.
• An echo is reflected sound. Sound reflects
from all surfaces.
• You see your face in a mirror because of
reflection. Light waves produced by a
source of light bounce off your face, strike
the mirror, and reflect back to your eyes.
Refraction
• The bending of a wave as it moves
from one medium to another is called
refraction.
Refraction and Wave Speed
• Remember that the speed of a wave
can be different in different materials.
• Refraction occurs when the speed of a
wave changes as it passes from one
substance to another
Diffraction
• Why can you hear music
from the band room
when you are down the
hall?
• You can hear the music
because the sound waves
bend as they pass
through an open
doorway.
• Diffraction is the
bending of waves around
a barrier.
Wave Interference
• The ability of two waves to combine
and form a new wave when they
overlap is called interference.
• When two waves overlap a new wave
is formed by adding the two waves
together.
Constructive Interference
• In constructive interference, a wave
with greater amplitude is formed.
Destructive Interference
• In destructive interference, a wave
with a smaller amplitude is formed.
• PS0499AA.avi
Friday, March 13, 2015
• Learning Target: I will understand the
properties mechanical of waves.
• Warm up
• Finish notes on wave behavior
• Mechanical Wave activity
Warm up – March 13
Create a concept map that shows the
relationship among the following:
• Wave, mechanical wave, electromagnetic
wave, compressional wave and transverse
wave (you will use this word twice)
•
Monday March 16, 2015
• Learning Target: I will determine if the
distance between wavelength will affect a
waves frequency.
• Warm up
• Compressional Wave Frequency Lab
(Domino Lab)
Warm up – March 16
Give me the following information on
Compressional Waves
• 3 – behaviors
• 2 – properties (parts of wave)
• 1 – How does the energy travel
Tuesday, March 17, 2015
• Learning Target: I will understand the
electromagnetic spectrum.
• Warm up
• Notebook check and vocab quiz
• Notes on Sound waves
• Notebook pages 188 – 190 (Due Friday)
Warm up – March 17
•
What is occurring in
these two diagrams? Give
the name of the behavior
and explain what is
occurring.
Sound
•All sound waves are produced
by something that vibrates.
•The vibrating object causes air
molecules to move back and
forth.
Making Sound Waves
• When an object vibrates, it exerts a
force on the surrounding air.
• As a result, a region where the air
molecules are closer together, is
created.
The Speed of Sound
• The speed of sound
is usually fastest in
solids, where
molecules are closest
together, and slowest
in gases, where
molecules are
farthest apart.
Material
Air
Speed
(m/s)
343
Water
1,482
Glass
5,640
Steel
5,960
The Decibel Scale
An increase of
10 dB on the
decibel scale
means the
intensity of a
sound has
increased by 10
times.
Amplitude and Loudness
• What’s the difference between loud
sounds and quiet sounds?
• The loudness of a sound is the human
perception of the intensity of the
sound waves that strike the ears.
• The greater the amplitude the more
energy and the louder the sound
Frequency and Pitch
• The pitch of a sound is how high or
low it sounds.
• Pitch corresponds to the frequency of
the sound. The higher the pitch is, the
higher the frequency is.
Echoes
• Sound reflects off of hard surfaces, just
like other waves do. A reflected sound
wave is called an echo.
The Doppler Effect
• The change in frequency that is due to
the motion of a source of sound is
called the Doppler Effect.
http://www.unitedstreaming.com/videos/dsc//externalApplications/simulations/Listen%20to%20the%20Whistle/index.html
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Ticket out the door
• What properties of a compressional wave
affects pitch and loudness?
Wednesday, March 18, 2015
• Learning Target:
• Warm up – Make church bells out of
hanger
• Notes on EM waves
• Homework – notebook pages 196 – 201
(due Friday)
Electromagnetic Waves
• Electromagnetic wave is a wave of
charged particles that can travel through
empty space or through matter
• Energy being transferred is radiant
energy.
EM waves
• Electromagnetic waves are made of two
parts
– Magnetic field
– Electric field
• EM waves travel
through space at
the speed of
light, 300,000 km/s
Electromagnetic Spectrum
• Electromagnetic spectrum is the wide
range of electromagnetic waves with
different wavelengths and frequencies.
• All waves in EM spectrum travel at same
speed (speed = wavelength x frequency)
Electromagnetic Spectrum
Radio Waves
• Longest wavelength; lowest frequency
(buildings – human)
• Uses: radio, cell phones, GPS, TV, aircraft
& shipping band, baby monitors, garage
door openers, wireless networks, radio
controlled doors
• Dangers - none
Microwaves
• Shorter wavelengths & higher frequencies
than radio waves (size of honey bee)
• Uses: microwave oven, radar,
communicate with satellites, astronomers
use to learn more about nearby galaxies
• Dangers: none
Infrared Waves
• Shorter wavelength & higher frequencies
than microwaves (pinpoint)
• Heat emitted by the sun
• Uses: Infrared binoculars and TV
controllers
• Danger – over exposure
Visible Light
• Narrow range of wavelengths and
frequencies that humans can see
(protozoan)
• Example: ROY G BIV (red, orange, yellow,
green, blue, indigo, violet)
• Red is longest wavelength (less energy);
purple is shortest (more energy)
• White light is all colors
combined.
Ultraviolet Rays
• Wavelength size of molecule; frequency
higher
• Stars emit UV radiation, most UV light
does not penetrate Earth’s atmosphere
• Great energy
UV Rays
• Positive effects – helps skin cells produce
vitamin D; produced artificially kills
bacteria on food and surgical instruments
• Negative effects – overexposure to UV
causes sunburn, skin cancer, eye damage,
wrinkles & premature aging of the skin
X-Rays
• Wavelength size of atom
• Frequency high energy wave
• Hot gases in universe emit X-rays
X-rays
• Use: x-ray bones and teeth
• Danger – over exposure to x-rays can
damage or kill living cells
Gamma Rays
• Wavelength size of atomic nuclei
• Frequency highest – radioactive material
• Supernova explosions, neutron stars and
pulsars, and black holes are all sources of
celestial gamma-rays
Gamma Rays
• Uses: Cancer treatment (kills cancer
cells) and surgical equipment (gamma
knife)
• Dangers – kills healthy cells also
Thursday, March 19, 2015
• Learning Target: I will understand the
properties of light and how these
properties help us see.
• Warm up
• Light Notes
• Light Worksheet
• Extra credit – EM superhero comic
(Friday, March 27)
Warm up – March 19
• As wavelength of an electromagnet wave
decreases how are frequency and energy
affected?
Light Ray
A light ray is a
narrow beam of
light that travels in
a straight line.
Light rays travel
away from a light
source.
Light and matter
• How do we see?
– Light from light source bounces off objects
and into your eyes
• 3 things happen to light waves that strike
an object
– some are absorbed by object
– some are reflected
– some pass through it
Opaque
A material that lets no light pass through.
Translucent
A material that allows only some light to pass
through.
Transparent
A material that allows
nearly all light to pass
through.
Why do objects have color?
• The color you see is the light wave that is
being reflected.
• White objects are reflecting all light waves
• Black object are absorbing all light waves
Primary light colors are
Red, green and blue.
Reflection and Mirrors
• Law of Reflection states that the angle of
incidence is equal to the angle of reflection
Plane Mirror
• Has a flat reflecting surface
• images are facing in opposite directions
• image seems to be coming from behind
the mirror.
Concave Mirror
Has a surface that is curved inward (like a
spoon).
Cause light rays to come together.
Can produce a focused beam of light (car
headlights).
Convex Mirror
Has a surface that is curved outward (back of
spoon).
Cause light waves to spread out.
Allows you to see a larger area.
Refraction and Lenses
• What is speed of light and how does it
change?
– Light can travel through empty space and
through a medium
– Atoms that make up materials slow the light
waves down
Speed of Light
Material
Air
Water
Glass
Diamond
Speed of Light
About 300 million m/s
About 227 million m/s
About 197 million m/s
About 125 million m/s
Lens
Transparent object with at least one curved
side that causes light to bend.
The amount of bending can be controlled by
making the sides of the lens more or less
curved.
The more curved the sides of a lens are, the
more light will bend after it enters the lens.
Convex Lens
Lens that is thicker in the center than at the
edges – light rays brought to a focus.
Microscopes use 2 convex lenses.
Telescopes use convex lenses.
Cameras use convex lenses.
Concave Lens
Lens that is thicker at the edges than in the
middle.
Light rays diverge.
Friday March 20, 2015
• Learning Target: I understand how light
interacts with various mediums.
• Warm up
• Notebook check page 188-190
• Finish Light WS
• Hand out study guide – due Tuesday
Warm up – March 20
• When you watch a bass drummer in a
marching band on the football field, you
see the drummer hit the drum before you
hear the sound. Explain
Monday, March 23, 2015
• Learning Target: I will be able to apply
wave properties and behaviors and
understand how they affect our lives.
• Warm up
• Turn in Light Review
• Study guide due tomorrow
• Unit review
Tuesday, March 24, 2015
• Learning Target:I will be able to apply
wave properties and behaviors and
understand how they affect our lives.
• Warm up
• Review Study guide
• Finish unit review
• Test is on Thursday
Warm up – March 24
• Describe how radio waves reach your ear.
(energy transformations)
Wednesday, March 25, 2015
• Learning Target: I will understand how
waves influence everything we see and
hear.
• Warm up
• Review for test
• Unit test tomorrow
Warm up – March 25
• Why can astronauts only communicate by
radio when working on the moon?