Wavelength, Crest, and Trough
Name
Wavelength, Crest, and Trough
By Cindy Grigg
Image credit NASA
Water waves are fun to
watch. Waves in the
ocean can be caused by
tides. They can be caused
by the wind. A wave is an
up and down movement of
water. When we talk
about waves, we use
special words to name
their parts.
The highest point of a wave is called the crest. The lowest point is
called the trough. Wave height is the vertical distance between the
crest and trough. Wavelength is the horizontal distance between
waves in a series. Wavelength can be measured between two wave
crests. It can be measured between two wave troughs.
The period of a wave is a length of time-the time it takes for
successive wave crests to pass a certain point. Velocity of the waves
can be calculated by dividing wavelength by time.
As waves get near the shore, water at the bottom of the wave is
slowed by friction with the ocean's bottom. As the wave slows, the
wavelength decreases. The crest and trough get closer together. The
wave height increases. The top of the wave is not slowed by friction.
It moves faster than the water at the bottom of the wave. The water
at the top outruns the water at the bottom of the wave. The water at
the top falls, creating a breaker. Breakers are ocean waves that break
up near the shore. Storms at sea can cause giant waves. The tallest
wave at sea was estimated to be one hundred twelve feet tall!
Questions
1. The highest point of a wave is called the ______.
A. period
B. wavelength
C. velocity
D. crest
E. trough
2. The lowest point of a wave is called the ______.
A. crest
B. wavelength
C. velocity
D. trough
E. period
3. The ______ of a wave is the time it takes for successive wave
crests to pass a certain point.
A. period
B. trough
C. velocity
D. crest
E. wavelength
4. ______ is the horizontal distance between wave crests or
troughs.
A. period
B. velocity
C. wavelength
5. How is the velocity of waves calculated?
Draw a series of waves. Label the parts.
Name
Write five facts you learned about waves.