Bellringer
Name three different types of waves.
Characteristics of
Waves
Part 1
Waves and Energy
• A wave is a type of mov’t that carries
energy from place to place. Energy is
what you need to do work.
• If you shake one end of a rope up and
down, a wave travels through the rope.
The wave in the rope carries energy
from your hand.
Waves and Energy
• A mechanical wave is a wave that
must have material to travel through.
The material a mechanical wave travels
through is called a medium.
• A wave is a rope is a mechanical wave.
The rope is the medium.
Waves and Energy
• Conversely, Electromagnetic waves
do not require a medium to transfer
energy.
• Visible light and radio waves are
examples of electromagnetic waves.
Waves and Energy
• A mechanical wave starts with a
vibration. A vibration is a repeated upand-down or back-and-forth movement.
• The vibration that starts a rope wave is
the up-and-down mov’t of your hand.
Types of Mechanical
Waves
• Transverse waves move the medium
up and down. A wave in a rope is a
transverse wave.
• Longitudinal waves move the medium
back and forth. A wave in a spring toy
(Slinky) is a longitudinal wave.
Parts of a Wave
• A transverse wave is composed of two
parts.
• A crest is the highest point of the wave.
• A trough is the lowest point of a wave.
Parts of a Wave
• A longitudinal wave is composed of two
parts.
• Compressions are the parts of the
wave that are closest together.
• Rarefactions are the parts of the wave
that are spread out.
Properties of Waves
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•
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Amplitude is how far the medium moves
when a wave passes through it.
For a transverse wave, amplitude is how far
the medium moves up or down. For a
longitudinal wave, amplitude is how far the
medium moves back or forth.
Amplitude shows how much energy the
wave has. The more energy the wave has,
the bigger the amplitude of the wave.
Properties of Waves
• Wavelength is how far a wave travels
before it starts to repeat. To find the
wavelength of a transverse wave, you
can measure the distance between the
crest of one wave to the crest of the
next wave. Or the distance between to
adjacent troughs.
• Wavelength is usually represented by
the Greek letter lambda (λ).
Properties of Waves
•
•
•
•
•
Frequency is the number of waves that go by a point in a
certain amount of time.
Frequency is measured in units called hertz (Hz). If one
wave passes a point each second, the frequency is 1Hz.
If two waves pass a point each second, the frequency is
2Hz.
Remember electricity, where 1 coulomb per second = 1
amp. This is known as current.
In waves, 1 wave per second = 1Hz. This is known as
frequency.
This is named after Heinrich Hertz, who is the German
scientist who discovered radio waves.
Properties of Waves
•Speed is how far a wave travels in a
given amount of time.
•For example, if a wave travels 5cm in 1
second, its speed is 5cm per second.
•Therefore,
•Speed = Wavelength x Frequency
•or
•speed (m/s) = λ (m) × f (Hz)
Wave Speed
s = Speed measured
in meters per second
(m/s)
s
f = Frequency
measured in Herts
(Hz)
λ f
λ = wavelength measured in meters
Wave Speed
• A wave has a length of 4cm, and a
frequency of 1 wave per second. What
is the wave’s speed?
Wave Speed
• A wave is found to be 3m long and
travels at 4 waves per second. What is
its speed?
Wave Speed
• A wave is traveling at 10 m/s and has a
length of 14 mm. What is the wave’s
frequency?