How many types of waves can you name? Chapter 16 Waves and Sound How many types of waves can you name?

A wave is a traveling disturbance. 16.1 The Nature of Waves A wave is a traveling disturbance. A wave carries energy from place to place.

Types of Waves (by medium) Electromagnetic Mechanical Creates disturbances in electric and magnetic fields Can travel through empty space ex light, x rays, UV Vibrates molecules Needs a medium to travel (propagate) Can not travel through empty space Ex. sound You can see the sun but you can not hear the sun!

Types of Waves (by direction of vibration) Longitudinal Transverse Particles vibrate ┴ to wave propagation Ex. Light Particles vibrate ∕∕ to wave propagation Ex sound

(aka compression wave) 16.1 The Nature of Waves Longitudinal Wave (aka compression wave) Particles vibrate ∕∕ to wave motion

16.5 The Nature of Sound Waves LONGITUDINAL SOUND WAVES

16.5 The Nature of Sound Waves The distance between adjacent condensations is equal to the wavelength of the sound wave.

16.5 The Nature of Sound Waves Individual air molecules are not carried along with the wave.

Does sound travel faster in a solid, liquid or gas?

The closer the molecules are, the faster the sound travels 16.6 The Speed of Sound Sound travels through gases, liquids, and solids at considerably different speeds. The closer the molecules are, the faster the sound travels

16.1 The Nature of Waves slow motion high angle wide shot of crowd doing "the wave" in Shea Stadium / Lon Transverse Wave Particles vibrate ┴ to wave motion.

over again by the source. 16.2 Periodic Waves Periodic waves consist of cycles or patterns that are produced over and over again by the source. In the figures, every segment of the slinky vibrates in simple harmonic motion, provided the end of the slinky is moved in simple harmonic motion.

In the drawing, one cycle is shaded in color. 16.2 Periodic Waves In the drawing, one cycle is shaded in color. The amplitude A is the maximum excursion of a particle of the medium from the particles undisturbed position. The wavelength is the horizontal length of one cycle of the wave. The period is the time required for one complete cycle. The frequency is related to the period and has units of Hz, or s-1.

16.5 The Nature of Sound Waves THE PRESSURE AMPLITUDE OF A SOUND WAVE Loudness is an attribute of a sound that depends primarily on the pressure amplitude of the wave.

Relationship between wavelength and frequency

The # of cars that pass per unit of time is the frequency f 16.2 Periodic Waves The # of cars that pass per unit of time is the frequency f

Example 1 The Wavelengths of Radio Waves 16.2 Periodic Waves Example 1 The Wavelengths of Radio Waves AM and FM radio waves are transverse waves consisting of electric and magnetic field disturbances traveling at a speed of 3.00x108m/s. A station broadcasts AM radio waves whose frequency is 1.230x106Hz and an FM radio wave whose frequency is 91.9x106Hz. Find the distance between adjacent crests in each wave.

16.2 Periodic Waves AM FM

16.5 The Nature of Sound Waves THE FREQUENCY OF A SOUND WAVE The frequency is the number of cycles per second. A sound with a single frequency is called a pure tone. The brain interprets the frequency in terms of the subjective quality called pitch.

4 Basic Wave Interactions 1- Interference 2- Diffraction 3- Reflection 4- Refraction

17.1 The Principle of Linear Superposition When two or more waves are present simultaneously at the same place, the resultant disturbance is the sum of the disturbances from the individual waves. Constructive vs Destructive Interference

Constructive Interference In phase (crest meets crest) Add together to form a bigger wave Pass through each other

Destructive Interference Out of phase (crest meets trough) Add together to form a smaller wave Pass through each other

17.2 Constructive and Destructive Interference of Sound Waves

Standing Wave Distance between successive nodes or antinodes is ½ λ Nodes- points of destructive interference. Antinodes- points of constructive interference Standing wave vs Moving Wave

17.5 Transverse Standing Waves Transverse standing wave patters.

Two overlapping waves with slightly different frequencies gives rise 17.4 Beats Two overlapping waves with slightly different frequencies gives rise to the phenomena of beats.

The beat frequency is the difference between the two sound 17.4 Beats The beat frequency is the difference between the two sound frequencies.

Resonance One vibrating object causes another object to vibrate at its natural frequency. Ex. Pumping your legs on a swing Shattering a glass with your voice Myth Busters Breaking Glass With Human Voice 33.wmv

Reuben’s Tube Tacoma Narrows Bridge Collapse Gallopin Gertie.wmv

Diffraction The bending of a wave around an obstacle or the edges of an opening is called diffraction.

Diffraction depends on the size of the wave and the size of the opening

2-D Wave Simulation

Wave Interference - Electric Field, Interference, Diffraction - PhET

LAW OF REFLECTION the angle of incidence equals the angle of reflection. Normal- imaginary line that runs perpendicular to the surface at the point of incidence θi = angle between the incident ray and the normal θr = angle between the reflected ray and the normal

There are two types of reflection Regular Reflection reflection off a smooth surface the reflected rays are parallel to each other. A mirror image is formed Diffuse Reflection reflection off a rough surface the reflected rays are scattered No image or a distorted image is formed

Which is regular and which is diffuse reflection?

The bending of light due to a change in speed Refraction The bending of light due to a change in speed

Index of Refraction The index of refraction of a material is the ratio of the speed of light in a vacuum to the speed of light in the material:

26.1 The Index of Refraction The slower light travels the higher the index of refraction The index of refraction is always greater than 1

What is the speed of light in diamond? v=1.24 x 108 m/s

What happens when light changes medium? When light travels from a less optically dense medium to a more optically dense medium, the velocity of the wave decreases. This causes the wave fronts to bunch up and the wavelength then decreases . However, the frequency of the wave remains constant.

Why does light bend?

Why does light bend? When the light meets the boundary at an angle, part of the wave front slows down while the other part is still moving quickly. This causes the light to bend.

SNELL’S LAW SNELL’S LAW OF REFRACTION When light travels from a material with one index of refraction to a material with a different index of refraction, the angle of incidence is related to the angle of refraction by

A ray of light is incident on a air water boundary at an angle of 35° What is the angle of refraction?

Which material has the larger index of refraction Which material has the larger index of refraction? The corn oil or the red jello?

Total Internal Reflection When light passes from a medium of larger refractive index into one of smaller refractive index, the refracted ray bends away from the normal. Critical angle

http://interactagram.com/physics/optics/refraction/

Dispersion In a dispersive media different wavelengths of light travel at different speeds therefore refract different amounts What color is always on the top of a rainbow? What color is always on the bottom?

Polarization Why can only transverse waves be polarized?

The Doppler Effect The Doppler effect is the change in frequency or pitch of the sound detected by an observer because the sound source and the observer have different velocities with respect to the medium of sound propagation. http://research.microsoft.com/en-us/um/redmond/groups/cue/soundwave/

Sonic Boom Meets Sun Dog on Vimeo http://video.google.com/videoplay?docid=-269376791712267206#docid=338907920311995235 Applet: Doppler Effect http://www.colorado.edu/physics/2000/applets/doppler2.html http://video.google.com/videoplay?docid=-269376791712267206#docid=-892292799726978663