What are waves?

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What are waves? Waves are rhythmic movements that carry energy through space or matter. Copyright © Houghton Mifflin Harcourt Publishing Company 3

Types of Waves Sound waves Light waves Electromagnetic waves Ocean waves Radiation Seismic waves Heat waves Transverse waves Longitudinal waves

There are two main types of waves Waves are classified by what they are travel through... SO…… There are two main types of waves Mechanical waves Electromagnetic waves

What are some types of waves? Waves such as water waves that require a medium are called mechanical waves. Copyright © Houghton Mifflin Harcourt Publishing Company 6

Mechanical Waves Some mechanical waves can travel through more than one medium. For example, sound waves can move through air, water, and a solid wall. Mechanical waves can’t travel without a medium. Copyright © Houghton Mifflin Harcourt Publishing Company 7

Electromagnetic Waves Electromagnetic (EM) waves are not disturbances in a physical medium. They are vibrations of electric and magnetic fields. Sunlight is an example of EM waves. Other examples include radio waves, microwaves, and X-rays. In empty space, all EM waves travel at the same speed, called the speed of light. Copyright © Houghton Mifflin Harcourt Publishing Company 8

a. produced by an oscillating object and a light wave is not.  A sound wave is different than a light wave in that a sound wave is a. produced by an oscillating object and a light wave is not. b. not capable of traveling through a vacuum. c. not capable of diffracting and a light wave is. d. capable of existing with a variety of frequencies and a light wave has a single frequency.

2 main ways to transfer energy Waves can be classified by comparing the direction that they cause particles in the medium to move with the direction in which the wave moves. Copyright © Houghton Mifflin Harcourt Publishing Company 10

How do waves transfer energy? Energy can be transferred from one object to another using compressions and rarefactions. This causes energy to travel in a longitudinal wave. Compressions – the energy is close together Rarefactions-the energy is separated Sound waves travel parallel Copyright © Houghton Mifflin Harcourt Publishing Company 11

How do waves transfer energy? Energy can be transferred from one object to another using up and down motions. This causes energy to travel as a transverse wave. In a transverse wave, particles move perpendicularly to the direction the wave travels. Copyright © Houghton Mifflin Harcourt Publishing Company 13

Characteristics of waves

Crests and Troughs The points where a wave is highest are called crests. The points where a wave is lowest are called troughs. Copyright © Houghton Mifflin Harcourt Publishing Company 15

Amplitude: Distance between “rest & crest” or “rest & trough” Gives indication of “power” or “strength” of wave Does not affect velocity of wave Determines loudness (sound) or brightness (EM wave)

Wavelength: Distance between any two repeating points on a wave crest-crest, trough-trough, expansion-expansion, compression-compression Determines what colors we see; what notes we hear (pitch) Shorter wavelengths have more cycles per minute because they aren’t as long

Velocity The rate at which energy travels Depends on the medium Mechanical waves travel faster through dense mediums EM Waves are faster through less dense mediums Frequency x wavelength

Frequency: number of wavelengths that pass any point per second measured in wavelengths/second or cycles/second Hertz (Hz) = number of wavelengths in 1 second Frequency is related to velocity: v = ƒ 

The distance between two corresponding parts of a wave is the wave’s a. amplitude. b. wavelength. c. frequency. d. speed.

The speed of a wave is its wavelength multiplied by its a. amplitude. b. vibration. c. frequency. d. reflection.

What is the frequency of a wave that has a speed of 0  What is the frequency of a wave that has a speed of 0.4 m/s and a wavelength of 0.020 meter? a. 10 hertz. b. 20 hertz. c. 0.008 hertz. d. 0.5 hertz.

What is the amplitude of this wave?

A wave travels through a medium because the medium’s particles are carried along with the wave. b. the wave’s energy passes from particle to particle. c. the medium transfers electromagnetic energy. d. the wave increases the potential energy of its medium.

The thunder is produced after the lightning. Why do you see lightning from a distant storm before you hear thunder? a The thunder is produced after the lightning. b Your eyes react faster than your ears. c Light travels faster than sound. d Sound travels faster than light.

a. amplitude. b. wavelength. c. frequency. d. speed. The distance between two corresponding parts of a wave is the wave’s a. amplitude. b. wavelength. c. frequency. d. speed.

If the distance from point A to point B in the diagram is 60 cm, then the wavelength is ____.