Waves
How many waves can you identify?
• You have just returned
home from a day at the
beach. You are hungry
from playing in the
ocean under the hot
sun. You microwave
some left over pizza.
The phone rings, and
you turn on the radio.
• List all the waves in
your new packet p 2.
What is a wave?
• A wave is a disturbance that transmits energy
through matter or space.
• A medium is a substance or material which
carries the wave.
P 3 Packet
• What is the difference between a mechanical
wave and an electromagnetic wave?
Energetic Waves
• Tie a rope to the back of your chair. Hold the
other end so that it is almost straight but not
tight.
• Move the rope up and down quickly to create
a single wave. Record your observations on
the left side of your INB.
• Which direction does the wave move?
• Compare the movement of the rope with the
movement of the wave.
• Where does the energy come from?
Put a piece of tape on the rope
• What direction does the tape move? Is it in the
same direction as the wave? Observe in INB
• Energy can be carried from its source by a wave.
But the material does not move with the energy.
• Ex leaf on water, sound in air.
• Which direction does the wave move?
• Compare the movement of the tape with the
movement of the rope with the movement of the
wave.
• Where does the energy come from?
Do Now
• How are light and sound alike? How are they
different? Use your Nature of Waves packet to
help you.
• On 2 pages (p 4) of your packet, make a
gigantic Venn diagram comparing the two.
Light
Sound
Two kinds of waves
• Longitudinal
• Transverse
Read Types of Waves, p 6-9, highlight 3 of the
most important things for each type of wave.
Longitudinal
• Vibrates parallel to (in the same direction of) wave
travel – The “LONG” way
– For example: sound waves
Animation courtesy of Dr. Dan Russell, Kettering University
– The other end of the medium moves without the actual
movement of matter.
Animation courtesy of Dr. Dan Russell, Kettering University
Longitudinal
• Use your Slinky to demonstrate a longitudinal wave:
– Work with a partner
– Stretch it out along the table
– One of you grasp and draw several coils of a stretched
Slinky toward yourself
– Release the coils
– The other student must hold his or her end of the Slinky
still
– A longitudinal wave pulse will be generated and travel
down the length of the Slinky.
Longitudinal
• Are composed of
– Compressions, where the parts of the medium
(coils of the Slinky) are closer together than
normal
– In this investigation, you created (generated)
compressional longitudinal waves
– The waves traveled through a media (the slinky)
Longitudinal
• Use your Slinky to demonstrate a longitudinal wave:
–
–
–
–
–
Work with a partner
Stretch it out along the table
One of you stretch a segment of the Slinky
Release the coils
The other student must hold his or her end of the Slinky
still
– A longitudinal wave pulse will be generated and travel
down the length of the Slinky.
Longitudinal
• Are composed of
– Rarefactions, where the parts of the medium are
farther apart than normal
– In this demonstration, you created (generated)
rarefactional longitudinal waves
– The waves traveled through a media (the slinky)
Transverse
• Vibrates perpendicular (at right angles) to the
wave travel
– An example of transverse waves are
Electromagnetic waves. Trans means across.
Animation courtesy of Dr. Dan Russell, Kettering University
Transverse
• Use your Slinky to demonstrate a transverse wave:
– Work with a partner
– One of you move your end of the Slinky back and forth
(left and right, like a snake crawling), perpendicular to its
stretched length.
– The other student must hold his or her end of the Slinky
still
– A series of transverse waves will be generated and will
travel through a medium (Slinky)
Reflection
• Complete your Venn diagram comparing
transverse waves and
longitudinal waves.
Electromagnetic Waves
• Are waves which are capable of transmitting
its energy through a vacuum (i.e., empty
space)
• Produced by the vibration of electrons within
atoms on the Sun's surface
• Travel through space until they reach Earth
• Examples are light and heat
• Are transverse waves which mean the
particles vibrate ACROSS the direction of the
wave
Mechanical Waves
• Are not capable of transmitting their energy
through a vacuum (space)
• Require a medium in order to transport their
energy from one location to another
Sound waves are mechanical longitudinal.
Mechanical Waves
• Waves traveling through a solid medium can
be either transverse waves or longitudinal
waves.
Water Waves
• A combination of longitudinal & transverse
Animation courtesy of Dr. Dan Russell, Kettering University
DO NOW
Sometimes people at a
sports event do “the wave”.
Do you think this is a real
example of a wave? Why or
why not? Quick Write on p
2.
Parts of a Wave
Read and Learn
Read the Nature of Waves handout p 10-12 and
define wavelength, amplitude, and frequency in
your notes on p 5 of packet.
Crest, trough and rest position are also
important terms.
• www.scilinks.org HSTP480, HST490
Parts of a Wave
1. Wavelength –
1. In transverse waves – distance between two crests or
troughs
2. In longitudinal waves – distance between two
compressions or rarefactions
2. Frequency – the number of waves that pass a point
in one second
1. Long wavelengths have low frequencies
2. Short wavelengths have high frequencies
3. Amplitude (wave height) – the distance from the
middle of a transverse wave to the crest or trough
Change amplitude!
• Hold a slinky on the floor between you and
your partner. Move one end from side to side
at a constant rate. The number of times you
move it from side to side is (back and forth)
each second is the frequency.
• Keeping the frequency the same, increase the
amplitude. How did the change in amplitude
affect the wavelength? Record in packet.
Change frequency!
• Now shake the slinky back and forth twice as
fast (double the frequency).
• What happened to the wavelength?
• Record in packet.
Summary
• Write 3 sentences showing how each property
changes the other: use the terms frequency,
amplitude and wavelength.