Waves
What is the motion of a combined wave?
A circle - In a combined wave, the motion of the medium is circular. So, each point of the spring moves in a circle as the wave is transmitted from left to right.
Trough
A trough is the opposite of a crest, so the minimum or lowest point in a cycle.
Compare the crests (high points) to the troughs (low points). What do you notice?
Crests are compressions (round) and troughs are rarefactions (pointy).
Increase density
Effect on wavelength - Get smaller Effect on wave speed - Decreases
Increase frequency
Effect on wavelength - Get smaller Effect on wave speed - Stays the same
Increase tension
Effect on wavelength - Stays the same Effect on wave speed - Increases
Increase amplitude
Effect on wavelength - Stays the same Effect on wave speed - Stays the same
Waves
Energy to travel from one place to another.
Frequency
Frequency (f) is equal to 1 divided by the period: f = 1/T. Frequency is measured in hertz (Hz), where 1 Hz = 1 cycle/sec.
Mechanical Waves
Have an x and y axis. (2-D)
Longitudinal Wave Motion
In a longitudinal wave, the motion of the medium is parallel to the direction of the wave. So, each point of the spring moves back and forth as the wave is transmitted from left to right.
Transverse Wave Motion
In a transverse wave, the motion of the medium (what the wave moves through—in this case, the spring) is perpendicular to the direction of the wave. So, each point of the spring moves up and down as the wave travels from left to right.
Wave Speed Formula
In general, the wave speed (v) can be calculated from the frequency (f) and wavelength (λ) using the formula v = f • λ.
Wavelength
Length of a wave (dinosaur symbol)
Frequency (f)
Number of waves per second (hz). 1 hertz = 1 wave/per second. F = 1/p
Surface
Particles move in circles.
Longitudinal
Particles move parallel to direction of energy.
Transverse
Particles move perpendicular to direction of energy.
What is the amplitude?
The amplitude of a transverse wave is the maximum distance a point on the wave is displaced, or moved, from its resting position.
Rest Position
The amplitude of a wave refers to the maximum amount of displacement of a particle on the medium from its rest position. In a sense, the amplitude is the distance from rest to crest. Similarly, the amplitude can be measured from the rest position to the trough position.
Amplitude
The amplitude, a, of a wave is the distance from the center line (or the still position) to the top of a crest or to the bottom of a trough. Be careful with this quantity - the center line is not always given in a diagram. Amplitude is measured in metres (m).
How would you describe the motion of a longitudinal wave?
The particles of a longitudinal wave are moving parallel to its wave motion.
How would you describe the motion of a transverse wave?
The particles of a transverse wave are moving perpendicular to its wave motion.
Wave speed
The speed of a wave is the distance a wave pulse travels per second. The wave speed is displayed below the spring.
Crest
The top of a wave (hill, highest place). A crest is the point on a wave with the maximum value or upward displacement within a cycle. A crest is a point on the wave where the displacement of the medium is at a maximum.
How do the wavelength, wave speed, and wave power of the combined wave compared to a transverse wave with the same settings? Explain.
The transverse wave ends up being more powerful than the combined wave, but the combined wave is more powerful than the longitudinal wave.
What factors influence the wavelength and speed of a wave?
The wavelength and speed of a wave can be influenced by many factors. Adjust the amplitude, frequency, tension, and density as described in the table below.
Longitudinal Wavelength
The wavelength of a longitudinal wave is equal to the distance between two successive compressions (or rarefactions).
How are the wavelength, frequency, and wave speed related?
They're all in the same equation.
How long does one cycle take?
This is the period (T) of the wave.
Period (p)
Time it takes for one wave to pass. Time (t) = (Dinosaur symbol) divided by velocity (v).
How is a wavelength measured? (Transverse)
Use the horizontal ruler to measure the horizontal distance between two crests. What is this distance?
Wavespeed
Wavelength times frequency. V = (wavelength divided by period).
Electromagnetic Waves
1). Electromagnetic waves don't need a medium. - What the wave travels through (LIM). - If they needed a medium, we wouldn't be able to see the Sun or stars. 2). Electromagnetic waves have an x, y, and z axis (3-D).
What are sound waves?
Sound waves are longitudinal waves that can travel through air.
