Tranverse and Longitudinal Waves
From High School Online Collaborative Writing
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[edit] Transverse and Longitudinal Waves
Transverse and Longitudinal waves can both be categorized under the term Mechanical Waves. Mechanical waves require a substance to travel through whereas electromagnetic waves like light don't. Examples of transverse and longitudinal waves are things like water waves, sound waves, or waves that travel along a spring or rope.
[edit] Transverse Waves
In a transverse wave the substance or ‘medium’ moves perpendicular to the direction of the motion of the wave. Transverse waves cannot propagate in a gas or a liquid because there is no mechanism for driving motion perpendicular to the propagation of the wave.
Each point on the string is just like a mass on a spring. The string is at an equilibrium position when the point lies on the straight line. If it is plucked away from its resting position the string will exert a force to restore its equilibrium position causing periodic oscillations. Plucking a string at one end causes periodic vibrations that eventually travel down the whole length of the string. If we connect one end of the string to a mechanism that moved the string up and down, lets say a little girl playing jumprope by herself, oscillation at one end of the string creates waves that propagate, or travel, down the length of the string. These are called traveling waves. The wave travels but the string only oscillates up and down.
See how this snakes body moves like a transverse wave. Pretty cool hu?
[edit] Longitudinal Waves
In a longitudinal wave the substance or ‘medium’ moves parallel to the direction of the motion of the wave.
A longitudinal wave can be created in a slinky. When the slinky is stretched out in a horizontal direction and the first coils of the slinky are vibrated horizontally. Each individual coil of the medium is set into vibrational motion in directions parallel to the direction which the energy is transported. Longitudinal Waves are referred to as sound waves because the particles that need to travel through the medium which transport the sound are transported by vibrating parallel to the direction which the sound moves. As the vibrating string moves in the forward direction, it begins to push upon surrounding air molecules, moving them to the nearest particle. This causes the air molecules to be compressed into a small region of space. As the vibrating string moves in the reverse direction it lowers the pressure of the air immediately. The lower pressure of the string causes air molecules in that region immediately to move to the right of the string to expand into a large region of space. The back and forth vibration of the string causes individual air molecules (or a layer of air molecules) in the region to move back and forth horizontally; the molecules move rightward as the string moves rightward and then leftward as the string moves leftward. These back and forth vibrations are imparted to adjacent neighbors by particle interaction; thus, other surrounding particles begin to move rightward and leftward, thus sending a wave to the right. Since air molecules (the particles of the medium) are moving in a direction which is parallel to the direction which the wave moves, the sound wave is referred to as a longitudinal wave.
See Caterpillars move like longitudinal waves, or like slinkys because they're cool!
[edit] Practice Problems
1. Compression waves in a spring are an example of
(1)longitudinal waves (2)transverse waves (3)polarized waves (4)torsional waves
2. A wave in which the vibration is at right angles to the wave's direction of motion is called a
(1)longitudinal wave (2)compressional wave (3)transverse wave (4)torsional wave
3. Which is an example of a longitudinal wave?
(1)gamma ray (2)X ray (3)sound wave (4)water wave
4. Which wave requires a medium for transmission?
(1)light (2)infrared (3)radio (4)sound
5. If a disturbance is parallel to the direction of travel of a wave, the wave is classified as
(1)longitudinal (2)electromagnetic (3)transverse (4)torsional
[edit] Answers to Practice Problems
1. Compression waves in a spring are an example of
(1)longitudinal waves
2. A wave in which the vibration is at right angles to the wave's direction of motion is called a
(3)transverse wave
3. Which is an example of a longitudinal wave?
(3)sound wave
4. Which wave requires a medium for transmission?
(4)sound
5. If a disturbance is parallel to the direction of travel of a wave, the wave is classified as
(1)longitudinal
[edit] Resources
Barron's Review Course Series, Let's Review: Physics The Physical Setting Regents Review Book. Transverse and Longitudinal Waves pg. 292-307
[edit] External Links
Transverse Waves This is a useful site because it shows through a video the different types of transverse waves. It is also hands on. Choose the amplitude and frequency.
Transverse And Longitudinal Waves This site shows moving diagrams of transverse and longitudinal waves.
