What’s in a wave? A wave is a repeating disturbance that transfers energy through a medium. A medium is the matter or space through which a wave travels (solid, Liquid, gas, vacuum) For example, during earthquakes, energy is transferred in powerful waves that travel through Earth The Nature of Waves

Making Waves 10.1 The Nature of Waves It is the up-and-down motion of your hand that creates the wave. In fact, all waves are produced by something that vibrates.

Waves and Matter 10.1 The Nature of Waves aves/shm.htm Waves are created by Simple harmonic motion

Energy is the ability to do work or cause change. Change Requires Energy 4.1 The Nature of Energy  Work is the transfer of energy that occurs when a force makes an object move

What does it mean to do work? Is doing homework work? Is holding a book doing work? Is pushing a block doing work? Change Requires Energy 4.1 The Nature of Energy No Yes

Waves and Energy Approaching waves bump the boat. Moving it up and down 10.1 The Nature of Waves

Waves and Energy Tsunami 10.1 The Nature of Waves Caused by earthquakes, volcanic eruptions, landslides or asteroids Up to 500 mph August 27, ,000 deaths December 26, ,000 deaths

Waves and Energy Sound Soundproofing- Layers of mats= Change kinetic to thermal Light Wearing black on a bright day 10.1 The Nature of Waves

Waves and Energy What happens to the energy as the wave travels? 10.1 The Nature of Waves Spreads out

Types of waves 10.1 The Nature of Waves Mechanical WavesElectromagnetic Waves What’s Moving? Mediums Order: fastest to slowest wave speed Examples Drawings Solids, liquids, gasses Vacuum, gasses, liquids, solids 3x10 8 m/s Particles of Medium Charges Sound, slinky Light, microwave, x-ray, ultraviolet

Types of waves 10.1 The Nature of Waves LongitudinalTransverse Mediums Order: Fastest to slowest Motion of particles compared to propagation of wave Picture: Label wavelength, amplitude, crest, trough, compression rarefaction Examples Solids, liquids, gasses Solids, liquids ParallelPerpendicular Sound, Traffic Jam Stadium wave, rope

Water Waves Water waves are not purely transverse waves The Nature of Waves A water wave causes water to move back and forth, as well as up and down. Water is pushed back and forth to form the crests and troughs.

Water Waves The low point of a water wave is formed when water is pushed aside and up to the high point of the wave The Nature of Waves

Water Waves 10.1 The Nature of Waves The water that is pushed aside returns to its initial position.

Water Waves 10.1 The Nature of Waves Ocean waves are formed most often by wind blowing across the ocean surface. The size of the waves that are formed depend on the wind speed, the distance over which the wind blows, and how long the wind blows.

10.1 Section Check Question 1 What is a wave? A wave is a repeating movement that transfers energy through matter or space. Answer

10.1 Section Check Question 2 Which is carried by a water wave? A. a boat on the surface B. boat anchor submerged 50 m C. energy D. water molecules

10.1 Section Check Answer The answer is C. Waves carry energy without transporting matter from place to place.

10.1 Section Check Question 3 Which type of wave does not need a medium? A. electromagnetic B. mechanical C. ocean D. sound

10.1 Section Check Answer The answer is A. Electromagnetic waves are made by vibrating electric charges and can travel through space where matter is not present.

The Parts of a Wave A transverse wave has alternating high points, called crests, and low points, called troughs Wave Properties

The Parts of a Wave On the other hand, a compressional wave has no crests and troughs. When you make compressional waves in a coiled spring, a compression is a region where the coils are close together Wave Properties

Wavelength A wavelength is the distance between one point on a wave and the nearest point just like it. For transverse waves the wavelength is the distance from crest to crest or trough to trough Wave Properties

Wavelength A wavelength in a compressional wave is the distance between two neighboring compressions or two neighboring rarefactions Wave Properties Symbol λ meters

Frequency and Period The frequency of a wave is the number of wavelengths that pass a fixed point each second. You can find the frequency of a transverse wave by counting the number of crests or troughs that pass by a point each second Wave Properties Frequency is f and expressed in hertz (Hz).

Frequency and Period The period of a wave is the amount of time it takes one wavelength to pass a point. As the frequency of a wave increases, the period decreases Wave Properties Period is T and has units of seconds.

Wavelength is Related to Frequency As frequency increases, wavelength decreases. The frequency of a wave is always equal to the rate of vibration of the source that creates it Wave Properties If you move the rope up, down, and back up in 1 s, the frequency of the wave you generate is 1 Hz.

Period is Related to Frequency As frequency increases, period decreases Wave Properties f= 1/T 1 f T

How quickly a wave moves through a medium The speed of a wave depends on the medium it is traveling through. V m/s 10.2 Wave Properties Wave Speed

Calculating Wave Speed You can calculate the speed of a wave represented by v by multiplying its frequency times its wavelength Wave Properties speed v v λ f

Amplitude and Energy Amplitude is the maximum distance a particle travels as a wave passes A meters 10.2 Wave Properties Amplitude is measured differently for compressional and transverse waves. Click image to play movie

Amplitude of Compressional Waves The closer the coils are in a compression, the farther apart they are in a rarefaction Wave Properties

Amplitude of Transverse Waves 10.2 Wave Properties The amplitude of any transverse wave is the distance from the crest or trough of the wave to the rest position of the medium.

10.2 Section Check Question 1 If a wave has a high point and a low point, is it a compressional or transverse wave?

10.2 Section Check Transverse waves have alternating high points, called crests, and low points, called troughs. Answer

10.2 Section Check Question 2 What is the wavelength of a wave?

10.2 Section Check Answer A wavelength is the distance between one point on a wave and the nearest point just like it.

10.2 Section Check Question 3 Which of the following refers to the number of wavelengths that pass a fixed point each second? A. frequency B. period C. wavelength D. wave speed

10.2 Section Check Answer The answer is A. Frequency is a length of time, and wavelength is a distance.