 # Characteristics of Waves

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Characteristics of Waves
Chapter 15, pages

What are Waves? A wave is a disturbance that transfers energy from place to place Waves travel through a material called a medium. Waves that require a medium to travel through are called mechanical waves.

What are 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.

Classification of Waves
Wave are classified according to how they move. Types of waves: 1. Transverse 2. Longitudinal 3. Surface

Transverse Wave In transverse waves, the particles of the medium move perpendicular in the direction of the wave. Parts of the transverse wave: Crest Trough Wavelength Amplitude

Longitudinal Wave In longitudinal waves, the particles of the wave move parallel to direction of the wave movement. Parts of the wave: Compressions Rarefactions Wavelength

Surface Wave Surface waves occur at the boundary between two mediums and are a combination of transverse and longitudinal waves.

A transverse wave….. Vibrates particles perpendicular to the direction of wave Vibrates particles parallel to the direction of the wave Vibrates both parallel and perpendicular to the direction of the wave Vibrates particles in one direction I don’t get it. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

Properties of Waves The basic properties of waves are amplitude, wavelength, frequency, and speed.

Amplitude Amplitude is the maximum distance the particles of the medium carrying the wave move away from their rest position. Measured from crest to resting position.

Wavelength Wavelength is the distance between corresponding parts of a wave. Wavelength is measured from crest to crest.

Frequency Frequency of a wave is the number of complete waves that pass a given point in a certain amount of time. Frequency is measured in hertz.

Wave Speed Wave speed is how far the wave travels in one unit of time, or distance divided by time.

Mathematical Relationship
The speed, wavelength, and frequency of a wave are related to each other by a mathematical formula: Speed=wavelength x frequency

In the diagram, identify the wave property “A”
Frequency Amplitude Wavelength I don’t know 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

Interaction of Waves When waves interact, three things can happen to the waves: Reflect Refract Diffract

Reflection Reflection happens when waves bounce off of a barrier.
The angle of incidence is the angle between the incoming wave and the imaginary perpendicular line. The angle of reflection is the angle between the reflected wave and the imaginary perpendicular line.

Law of Reflection The angle of reflection is equal to the angle of incidence.

Refraction Refraction occurs as the wave go between different mediums.
The speed of a wave changes as the medium changes. The change in speed of the wave causes the waves to bend.

Diffraction Diffraction is the bending of waves as the waves go through a small opening or around a corner. As the wave goes through the hole or around the corner, it spreads out and bends.

Interference Interference occurs as two or more waves interact.
Constructive interference happens when waves meet and the amplitude increases. Destructive interference happens when waves meet and the amplitude decreases.

Standing Waves Standing waves form as the original wave is interfered with by the reflected wave. The standing wave has a node and an antinode.

Review Questions What do we call the transfer of energy from place to place? (wave) What do we call the material through which waves travel? (medium) When the medium _______________, a wave is created. (vibrate) How are waves classified? (how they move)

Review Questions The highest part of a transverse wave is called the _______________. (crest) The lowest part of a transverse wave is called the _______________. (trough) What type of wave travels parallel to the direction of the wave travel? (longitudinal) What type of wave travels perpendicular to the direction of the wave travel? (transverse)

Review Questions What type of waves is on top of a pond or lake?
(surface) What property of a wave is the maximum distance that particles of the medium move from resting position? (amplitude) What do we call the distance between two corresponding parts of a wave? (wavelength) In what units is frequency measured? (hertz)

Review Questions What is the mathematical relationship between speed of a wave, frequency and wavelength? (speed = wavelength x frequency) When a wave hits a barrier and bounces back, it is called _______________. (reflection) When a wave bends because it changes speed as it travels through different mediums, it is called _______________. (refraction) When a wave bends as it travels around the edge of a barrier it is called _______________. (diffraction)

Review Questions The interaction between two waves is called ________________. (interference) Waves combine to make a wave of larger amplitude is called ______________. (constructive interference) Waves combine to make a wave of lower or no amplitude is called _______________. (destructive interference) What type of wave are two waves that interfere with each other as they pass each other? (standing)

Review Questions What occurs when the vibration matches the natural frequency of the object? (resonance) What are the highest and lowest points called on a standing wave? (antinodes) What are the points of zero amplitude called on a standing wave? (nodes) What type of waves does an earthquake produce? (seismic)

Review Questions Longitudinal seismic waves are called _______________. (primary) Transverse seismic waves are called _______________. (secondary) Which type of seismic wave causes the most damage? (surface) Which seismic wave is the fastest?

Review Questions What type of waves requires a medium to pass through?
(mechanical) What name is given to the waves produce by underwater earthquakes? (tsunamis) What machine measures ground movement? (seismograph) What scale is used to measure the magnitude of seismic waves? (Richter)

Review Questions What are the areas of a longitudinal wave where the waves are close together? (compressions) What are the areas of a longitudinal wave where the waves are far apart? (rarefactions) What is the angle defined by an incoming wave and the imaginary perpendicular line? (angle of incidence) What is the angle defined by a reflected wave and the imaginary perpendicular line? (angle of reflection)

Review Questions What is the relationship between the angle of incidence and the angle of reflection? (they are equal to each other)