Properties of Waves
EQ: How do I describe the basic properties of waves and how a wave’s speed is related to its wavelength and
frequency?
Vocabulary
Crest - The highest point, or peak, of a wave.
Trough -The lowest point, or valley, of a wave.
Properties of Waves
• There are four wave properties– Amplitude– Wavelength– Frequency– Speed
water level at rest
fixed point
crest
trough
Frequency is the number of wavelengths passing a fixed point in a certain amount of
time, usually 1 second.
Wavelength is the distance from one crest or trough to the next.
Amplitude is the distance a medium moves
above or below its position at rest.
Means crest in a transverse wave
Means trough in a
transverse wave
Amplitude
The maximum distance that a disturbance causes a medium to move from its rest position; the distance between a crest or trough of a wave and line through the center of a wave.
Rope example: move your hand up and down at a greater distance, increases the amplitude. Uses more energy.
Slinky – high vibrations cause the compressions to be more crowded and rarefactions loose giving the slinky higher amplitude.
Which wave has a greater amplitude?
Which longitudinal wave has the larger amplitude?
Not very crowded
crowded
Wavelength
• The distance between two corresponding parts of a wave
Frequency• The number of complete waves that pass
a given point in a certain amount of time or the number of vibrations per second.
• Hertz (Hz) – measures frequency. A wave that occurs every second has a measurement of 1 Hz. If two waves pass you every second then the measurement is 2 Hz
• Example – if you move your hand slower, decreases frequency, move it faster increases frequency.
Speed
• Waves in different mediums travel at different speeds– Ex. Light and sound- see a flash of lighting,
hear a clap of thunder– Speed, wavelength and frequency related to
each other by the formula
Speed = wavelength x frequency
F = S W = S
W F
Go Figure
• The speed of a wave on a rope is 50 cm/s and its wavelength is 10 cm. What is the frequency?
• What is the speed of an object that travels 6 meters in 2 seconds?
• The speed of a wave on a guitar string is
100m/s and the frequency is 1000 Hz. What is the wavelength of the wave?
Class Work Homework
• Fill in– What did I learn– Confused– Say
– Read Section 1-2 in your textbook
Worksheet