How does one differentiate between transverse and longitudinal waves? 7.11.6

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Waves. How does one differentiate between transverse and longitudinal waves? 7.11.6. Wave. Waves are a disturbance that transfers energy from place to place. Waves can be Transverse, Longitudinal (Compressional), or Electromagnetic.

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Waves

How does one differentiate between transverse and longitudinal waves?

7.11.6

Wave
• Waves are a disturbance that transfers energy from place to place.
• Waves can be Transverse, Longitudinal (Compressional), or Electromagnetic.
Mechanical Waves
• Waves are created when a source of energy causes a medium to vibrate.
• A vibration is a repeated back and forth or up and down motion.
Mechanical Waves
• Can be transverse or longitudinal.
• All mechanical waves need a material medium to shake vibrate.
• The wave medium is not the wave and it doesn't make the wave; it merely carries or transports the wave from its source to other locations.
• A medium can be a gas, liquid, or solid.
Transverse wave
• Transverse means across.The highest parts are called crests the lowest parts are called troughs.
• A wave in which the motion of the medium is perpendicular to the motion of the wave.
• The motion of the medium is up and down. The motion of the wave is right or left.
• This movement creates right angles to the direction in which the waves are traveling.

Example: Seismic Secondary (S) waves

Compressional Wave
• Matter vibrates in the same direction as the wave travels.
• The motion of the medium is left or right.
• The motion of the wave is left or right.
• Sound waves are longitudinal. The air vibrates back and forth along the same direction as the wave is traveling.
Compressional /Longitudinal Wave
• Rarefactions, where the parts of the medium are farther apart than normal (troughs).
• Compressions, where the parts of the medium (coils of the Slinky) are closer together than normal (crests).

ElectromagneticWaves

Not all waves require a medium to travel.

Light from the sun travels through empty space.

Electromagnetic Waves
• EM waves are transverse waves consisting of changing electric fields and magnetic fields.
• EM waves do not require a medium. They travel through a vacuum, or empty space, as well as through matter.

• Electromagnetic radiation behaves like a wave and like a particle.
How are EM waves produced?
• Electric Field
• Exerts electric force on charged particles. They can be produce by changing magnetic fields
• Magnetic Field
• Exerts magnetic forces and can be produced by changing electric fields.
• Electromagnetic waves are produced when an electric charge vibrates or accelerates. In other words it is produced in constantly changing fields.
How do they travel?
• The fields regenerate each other.
• The magnetic and electric fields of an electromagnetic wave are perpendicular to each other and to the direction of the wave.

http://www.walter-fendt.de/ph14e/emwave.htm

z

Direction of Propagation

y

Magnetic Field

Electric Field

x

Electromagnetic Waves
• There are different types of electromagnetic waves
• Infrared waves
• Visible light waves
• Ultraviolet light waves
• X-rays
• Gamma rays
• These waves can travel through air, through the walls of your house, and even to your TV and radio.

Properties of Waves

Basic Properties of Waves
• Amplitude
• Wavelength
• Frequency
• Speed
Amplitude
• Amplitude is the maximum distance the particles of the medium carrying the wave move away from their rest positions.
• The farther the medium moves as it vibrates the larger the amplitude of the resulting waves. The greater the amplitude the greater the amount of energy
Amplitude of transverse waves
• The amplitude of a transverse wave is the maximum distance the medium moves up or down from its rest position. You can find the amplitude of a transverse wave by measuring the distance from rest to crest or rest to trough.
Amplitude of a longitudinal wave.
• The amplitude of a longitudinal wave is a measure of how compressed or rarefied the medium becomes.
Wavelength
• A wave travels a certain distance before it starts to repeat. The distance between two corresponding parts of a wave is its wavelength.
• Transverse measure from crest to crest or trough to trough.
• Longitudinal measure from one compression to the next.
Frequency
• The number of complete waves that pass a given point in a certain amount of time.
• AKA number of vibrations per second.
• Frequency measured in hertz (Hz).
Speed
• The speed, wavelength, and frequency of a wave are related to each other by a mathematical formula.
• Speed = wavelength x frequency
• Frequency = speed/wavelength
• Wavelength = speed/frequency
Speed
• Waves in different mediums travel at different speeds. However, in a given medium and under the same conditions the speed of the wave is constant.
Ways Waves Interact
• Reflection
• Refraction
• Diffraction
• Interference
• Constructive
• Destructive

Standing Waves

Reflection
• When an object or wave hits a surface through which it cannot pass, it bounces back.
• Angle of incidence
• Angle of reflection
Examples of reflection
• Mirror
• Echo
• Ball against a wall

Refraction is when a wave moves from one medium into another medium at an angle, it changes speed as it enters the second medium which causes it to bend. The bending of waves due to a change in speed is called refraction.

Refraction
• Though all waves change speed when they enter a new medium. Bending occurs when one side of the wave enters the new medium before the other side
Diffraction
• When a wave passes a barrier or moves through a hole in a barrier it bends and spreads out.
Interference
• Constructive interference occurs whenever two waves combine to make a wave with a larger amplitude.
• Destructive interference when the amplitudes of two waves combine producing a smaller amplitude.
Standing waves:
• If the incoming wave and the reflected wave combine at the right places the combined wave appears to be standing still.
• It appears to be standing in one place, even though it is two waves interfering as they pass through each other.
Nodes: at certain points, destructive interference causes the two waves to combine and produce an amplitude of zero.

Antinodes are the points of maximum energy. The crests and troughs of a standing wave.

Nodes and Antinodes
Resonance
• Most objects have a natural frequency of vibration. Resonance occurs when vibrations traveling through an object match the object’s natural frequency.
• An object that is vibrating at its natural frequency absorbs energy from the objects that vibrate at the same frequency. Occurs in music.