Lesson Plan #:AELP-PHY0049
An AskERIC Lesson Plan
AUTHOR: Vilia Natchez; Our Lady of Snows, NV
GRADE LEVEL/SUBJECT: 3-5 Waves
Sound, water and light travel in waves. All three have troughs and crests.
Sound is a disturbance of air waves with pitch. Water waves travel in a
circle away from the source of disturbance. Light waves travel in a straight
line unless they meet an obstacle.
Experiments in this unit may be built upon or deleted in order to fit
the time frame (1-3 lessons) desired.
The purpose of this lesson is to give children a basic understanding
of the physical properties of waves without becoming too technical.
Children are to understand the terms "crest " and "trough" as
related to waves. They are to use a hands-on method using toys to become
aware that waves are in air, water and light.
RESOURCES/MATERIALS: (* items indicate items needed per group)
ACTIVITIES AND PROCEDURES:
1 toy xylophone
* 5-6 test tubes mounted in a rack (jars/glasses)
empty containers (boxes, plastic cups, lids)
* 6-8 yd. masking/strapping tape
1 glass pie pan
1 food color (2-3 drops)
1 overhead projector
* plastic straws (80-100)
* bottled soap bubbles with wand (1)
* 1/4 cup clay (approx.)
* toothpicks (approx. 12)
1 flat pan
* aluminum foil (3x3") square
* straight pins (1)
1 lamp (no shade) or flashlight
A demonstration is made with a slinky. Ask children to define the part
they think of as a crest and that part which is a trough. Draw a simple
diagram on the board, labeling each. A dictionary could be used. Explain
that all waves have crests (ups) and troughs (downs).
Crests and Troughs in Sound Waves
Crests and Troughs in Water Waves
Tune in two radios to the same station. Place them about 50 cm apart. Have
children walk quietly about the room listening for dead spots (troughs)
and loud spots (crests). They could be encouraged to raise a hand when
they hit a trough.
Listen to different pitches on a toy xylophone. Ask why they think it sounds
different. They should be allowed to try the ready-made xylophone, then
make their own. A xylophone is easily made by pouring different levels
of water into a rack, by using identical jars, etc. . After trying both
the ready-made and the homemade versions, they should be guided to conclude
that the length of bar or height of water can regulate the pitch of sound
Rubber bands of various thicknesses can be stretched across boxes or any
small, empty containers. See if they can make graduated sounds as in a
xylophone. Conclusion: The tighter a band is stretched, the faster it vibrates
and makes a higher sound.
Crests and Troughs in Light Waves
A glass pie pan is mounted on an overhead projector. It is filled with
water tinted with food coloring. Waves can be demonstrated by touching
a rod/pencil to the center of the water and watching the waves (troughs
and crests) move to the edge of the pan and back. Try two rods to see what
happens when the waves meet. Encourage the children to try it. Ask if they
have ever seen this happen before. Relate this to a rock thrown into a
pond or a toy into a swimming pool.
Wave machines can be made by groups of children to demonstrate what they
did in the above experiment. It also simulates ocean waves. A strip of
tape (3-4 ft.) is laid on a table sticky side up. A child should hold each
end securely. Others in the group will place the middle of a straw each
half inch in the middle of the tape. When all straws are laid, the second
strip of tape is placed on top of the straws (sticky side down) and above
the first strip of tape. The finished product will resemble a spine (tape)
and ribs (straws). A child holds each tape end horizontally while a third
child pushes down on one end of the wave machine's straws allowing a wave
pattern to go from one end of the straws to the other. Be sure to look
for waves and troughs!
TYING IT ALL TOGETHER:
Blow bubbles with the wand. Look for colors in them. Why are they colored?
Explain that light waves travel in a straight line unless something interferes
with them. Since bubbles are round and not straight, light waves get bent
when they hit the bubble. Many bending waves cause color.
Give each child or group a small square of aluminum foil (3x3) and a straight
pin. Instruct them to make two tiny holes near the center of the foil about
1/2cm apart. A bright light source without a shade (lamp, flashlight) should
be set in front of the room and all other lights turned out. The children
should hold the foil about one foot in front of their eyes. Closing one
eye and looking through both holes, they should see one light source diffusing
crests and troughs of light.
The last experiment could be related to math in that it requires the children
to guess the number of planes that are in a constructed object. They might
start by constructing a simple square. This is easily achieved by placing
four small balls of clay so they are connected with four toothpicks forming
a square. Ask how many planes (flat surfaces) are in the figure. When they
have made suggestions, dip the figure into a pan of the bubbles. Lifting
it carefully, one plane can be observed. Their next figures can be more
complex (3-D) which will make plane estimates more complicated. Always
be aware of the light waves visible on each plane.
This is a series of very simple hands-on experiments which will
introduce children to the idea that waves have troughs and crests. They
should be comfortable with those terms even though they don't remember
those of " bending" or "diffusion". It will be a firm base for physics
in their later years.
These lesson plans are the result of the work of the teachers who have
attended the Columbia Education Center's Summer Workshop. CEC is a consortium
of teacher from 14 western states dedicated to improving the quality of
education in the rural, western, United States, and particularly the quality
of math and science Education. CEC uses Big Sky Telegraph as the hub of
their telecommunications network that allows the participating teachers
to stay in contact with their trainers and peers that they have met at
This activity has been copied, with permission, from the
Educational Resources Information Center (ERIC) server to ours, to
allow faster access from our website. We encourage you to explore the
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