3. What is a wave?
A vibration or disturbance.
SOUND & LIGHT are forms of energy
that travel in waves.
4. Period (T)
A period is the time it takes for one
cycle.
1 cycle = 1 complete trip
1 trip back & forth
Around and back to the same point
1 wave = 1 cycle
5. Frequency (ƒ)
# of cycles in one second.
# of waves in one second.
Measured in Hertz (Hz).
1 Hz = 1 cycle per second
7. Give it a try…
A wave vibrates 100 times in 2
seconds. What is its frequency?
100 waves in 2 seconds
100 waves per 2 seconds
50 waves/ 1 second
50 waves/ second = 50 Hz
8. Give it a try…
The Sears Tower moves back and forth
at a frequency of about 0.1 Hz. What is
its period?
ƒ = 0.1 Hz
T = 1/ ƒ
T= 1/ 0.1 Hz
T= 10 sec
10. Parts of a wave
Crest= High point of a wave.
Trough=Low point of a wave.
Amplitude (A)= Distance from the
midpoint to the crest.
Wavelength (λ)= The length of one
complete wave.
11.
12. Wavelength (λ)
The length of one wave is measured
from a point on one wave to that same
point on the next wave.
Crest to crest
Trough to trough
Midpoint (past crest & trough) to midpoint
13.
14. Speed of a wave
The speed of a wave depends on the
medium it travels through.
Medium is the material it passes
through.
16. What is the velocity of a wave that is 2 m
long with a frequency of 10Hz?
λ = 2m
ƒ = 10Hz
ν = λ • ƒ
ν = (2m)(10Hz)
ν = 20m/s
17. Types of waves
Transverse:
The medium moves at a right angle to the direction of
the wave.
Example: Light
18.
19. Types of Waves
Compressional
A Compressional
wave is when matter
vibrates in the same
direction as the wave
travels.
These are also
known as
Longitudinal
waves.
20. Longitudinal:
The medium moves in the same direction as
the wave.
Example: Sound waves
21. Parts of a Compressional
Wave
Compression: where the wave
“squeezes” or compresses the medium
Rarefraction: Where there is space in
the wave with no compression.
22.
23.
24.
25. Type of medium
The type of medium changes the way a
wave moves.
Mediums with close molecules travel
quickly.
This is why waves travel better in liquids
and solids than in gases.
26. Waves through air
However, air can still let waves pass at a
great speed.
The speed of sound through air is 344 m/s!
That is really fast!
27. What happens to a wave
when it runs into something?
REFLECT- Bounce off
REFRACT- Bend
DIFFRACT- Break up
GET ABSORBED- Soak into
PENETRATE- Pass through
29. How does sound travel?
Sound is a form of energy that moves in
waves through matter.
Sound waves are longitudinal waves
or compressional waves .
30. Properties of Sound Waves
Sound waves move out from a
vibrating object in all directions.
As a sound wave travels further from the
object, the wave gets weaker.
31. How is sound produced?
The movement of particles around a
vibrating object creates a sound
wave.
Your vocal cords vibrate air molecules.
They vibrate other air molecules and so
on until the air molecules by the listener’s
ear vibrate their ear drum.
32. Speed of sound
The speed of sound in air at room
temperature is about 344 m/s.
vSound in Air = 344 m/s
33. Speed of Sound
If the particles are closer together, they
hit faster and the wave (sound) moves
faster.
Does sound move faster in:
air or water?
water or steel?
34. When one particle bumps another that
bumps another and so on, a sound is made.
IS THERE SOUND IN SPACE?
35. LOUD and soft Sounds
Intensity: strength of a sound
Which sound is more intense, an airplane or talking?
Which has more energy?
Intensity is measured in Decibels.
Your ear hears intensity as volume of a sound.
36. Intensity of a wave
The intensity of a wave is shown by the
amplitude.
An intense sound is LOUD so it has a
high amplitude.
LOUD SOFT
37. and sounds
The pitch describes
high and low
sounds.
A high sound like a
flute has a high pitch.
A low sound like a
tuba has a low pitch.
38. Pitch of a wave
The pitch of a wave is shown by the
frequency.
A high pitch sound has a high
frequency and a short wavelength.
39.
40. ECHOS
When sound waves reflect, they make an
echo.
Sonar uses echo to locate objects under
water.
Ultrasound uses echos to “see” inside the
human body.
45. Look at your pictures and answer
the questions:
Which ELECTROMAGNETIC WAVE has
the most energy? The least?
Which ELECTROMAGNETIC WAVE has
the longest wavelength? The shortest?
As frequency increases, what happens to
energy?
As frequency increases, what happens to
wavelength?
As the wavelength increases, what happens
to the frequency of the waves?
47. Radio Waves
Radio waves are
used for radio
broadcasts, amateur
radio, television, and
mobile phones.
48. Microwaves
Microwaves can be
used to study the
Universe,
communicate with
satellites in Earth
orbit, and cook
popcorn.
49. Infrared Waves
Infrared waves are
used to heat food at
restaurants, by
police scanners, in
your remote control.
50. Ultraviolet Waves
UV Waves are used
in tanning and in
sterilization of
equipment.
51. X-Ray Waves
X-Rays are so
strong, they can go
right through you!
52. Gamma Waves
Gamma rays and X-
Rays can cause
cancer, but gamma
rays can also be used
to destroy cancer cells:
this is called radio-
therapy or radiation.
53.
54.
55.
56. LIGHT WAVES- Visible Light
VISIBLE LIGHT is a
form of
electromagnetic
energy that we can
see.
65. How does light travel?
Light is made up of bunches of energy
called photons.
Light travels in waves.
Light is an example of a transverse
wave.
66. Speed of light
Light travels fastest through empty spaces.
Light waves slow down or get stopped by
matter.
In air at room temperature, speed travels at:
v = 300 000 km/s = 3 X 108m/s
Remember, sound travels at 344 m/s, so light
is about 1,000,000 times faster!
69. Materials that light hits can be:
Opaque- (Solid)
Does not let light pass through.
A door is opaque.
Transparent- (See-through)
Lets light pass through.
A window is transparent.
Translucent- (Not clear)
Lets some light pass through.
A glass of lemonade is translucent.
70. When light hits a material, the
light may:
Reflect: Bounce off
Refract: Bend
Get Absorbed
72. Law of Reflection
The angle the light ray hits the mirror
equals the angle it bounces off.
The angle of incidence equals the angle
of reflection.
99. When ALL of the colors of light
combine…
White light is produced.
100.
101. The Sun gives off "white" light, a mixture of all the colors in the spectrum.
The object looks WHITE because an equal mixture of RED, BLUE, and GREEN
light is reflected off the object and interpreted by our eyes and brain as WHITE.
102. You can use a FILTER to
absorb a color of light.
103. Your TV works using little
pixels that look like this:
Any color can be made from a
combination of these three colors of
light.
105. Colors effect our mood!
Red = Stimulating
Yellow = Excitement
Blue = Calming
Which would you eat?
106. Colorblindness
Some people have trouble telling the
difference between colors.
Their rods and cones do not detect
differences.
107.
108.
109. The last test is the easiest to use.
A person with normal color vision
will see a “5” in the dot pattern.
A person with Red/Green color
blindness (the most common) will
see a “2” revealed in the dots.
110. Sometimes your eyes get
tired!
Your rods & cones get used to what
they see and it takes them some time to
go back to normal.