ch25_jdmk

=Chapter 25 Review = ="Vibrations and Waves" =

QUICK VOCAB: **vibration- a wiggle in time that must move back and forth ** **wave** - a wiggle in space and time that must extend from one place to another =__**25-1:Vibration of a Pendulum ** //Pages 372 – 373//__= =A period of the time it takes for a back-and-forth swing. Galileo discovered the period of a swinging pendulum depends on the length of the pendulum and the acceleration of gravity. A shorter pendulum has a shorter period than a longer one. You will notice people with longer legs tend to walk with a slower stride than people with shorter legs.=

=__**25-2: Wave Description** //Pages 373 – 375//__= = Simple harmonic motion - the back-and-forth vibratory motion of a swinging pendulum, often called oscillatory motion = = frequency-hertz(Hz)- unit of frequency named after Heinrich = = sine curve- curve whos shape represents the crests and troughs of a wave = = crests- highest point of the wave = = troughs- lowest point of the wave = = amplitude- distance from the midpoint to the crest / trough = = wavelength- distance from the top of one crest to the top of the next = = =

**With frequency, one back-and-forth vibration is one cycle. Freqency is measured in herts(Hz) after Heinrich Hertz. Higher frequencies can be measured in kilohertz, megahertz or even gigahertz!** Frequency = 1 / period

=__**25-3: Wave Motion** //Pages 375 - 376//__= =Sound and light both come through waves. When energy is transferred, there is no transfer of matter, the disturbance moves. Waves are disturbances in their mediums, and energy transferred by a vibrating source is carried by a disturbance.= =__**25-4: Wave Speed **//Pages 376 – 377//__= =The speed of a wave depends on it's medium and the speed, frequency and wavelength are related. The following formula works for all types of waves.= Wave speed = frequency x wavelength  <span style="font-size: 12pt; font-family: "Times New Roman"; color: rgb(51, 153, 102);"> <span style="font-family: Times New Roman; display: block; font-size: 130%; color: rgb(255, 0, 255); text-align: center;"> <span style="font-size: 12pt; font-family: "Times New Roman"; color: rgb(51, 153, 102);"> <span style="font-family: Times New Roman; display: block; font-size: 156%; color: rgb(51, 153, 102); text-align: center;"> V = f <span style="font-size: 15.5pt; font-family: "Times New Roman"; color: rgb(51, 153, 102);">λ

Sounds of instruments all reach you at the same time. Low frequencies have long wavelengths and high frequencies have shorter wavelengths. =__**<span style="color: rgb(9, 91, 251);">25-5: Transverse Waves ** //Page 378//__= =transverse wave- whenever the motion of the medium is at right angles to the direction in which a wave travels= All of the following have transverse waves : stretched strings of musical instruments, surfaces of liquids, electromagnetic waves making up radio waves and light, and seismic waves. = = =__<span style="color: rgb(9, 91, 251);">**25-6: Longitudinal Waves** //Pages 378 - 379//__= =longitudinal wave- a wave in which the particles move //along// the direction of a wave rather than at right angles to it = = = =__<span style="color: rgb(9, 91, 251);">**25-7: Interference** //Pages 378 - 379//__= =interference pattern- waves overlap to form this pattern= =constructive interference(reinforcement amplitude)- when the crests of two waves overlap and the individual effects add together, forming increased amplitude= =destructive interference(cancellation)- when the crest of one wave overlaps the trough of another and the high part of one fills the low part of another, reducing the individual effects= More than one vibration or wave causes interference. Where you see the gray lines shows the crests of one wave overlapping the troughs of another. Interference works with all wave motion. = = =__<span style="color: rgb(9, 91, 251);">**25-8: Standing Waves** //Pages 380 - 382//__= =standing wave- results from interference betwen an incident and reflected wave, wave appears not to be traveling= =nodes- part of standing wave that remains stationary= =antinodes - positions on a standing wave with the largest amplitudes=

Interference causes standing waves. Waves are out of phase at the nodes. You can create standing waves by changing frequencies. Standing waves are apparent in both transverse and longitudinal waves.

= = =__<span style="color: rgb(9, 91, 251);">**25-9: The Doppler Effect** //Pages 382 - 384//__= =Doppler effect - the change in frequency of a wave due to the motion of the source or the reciever= =blue shift- an increase in frequency= =red shift- a decrease in frequency= The Doppler Effect is greater when the speed is greater. This is shown through a car approaching you then passing you. While approaching, the pitch is higher. When it passes, the pitch drops. It all depends on how frequently the wave crests and encountering you. Light source approaching experiences an increase in frequency and light source leaving has a decrease in frequency. These are both in the above terminology, blue shifts and red shifts. = = =__<span style="color: rgb(9, 91, 251);">**25-10: Bow Waves** //Pages 384 - 385//__= =Bow wave- the v-shaped wave produced by an object moving on a liquid surface faster than the wave speed= Bow waves start when the speed of a source is as great as the speed of the waves it creates. Wave crests overlap and harm the air over the wings. When it travels faster than the speed of sound it is considered to be supersonic. = = =__<span style="color: rgb(9, 91, 251);">**25-11: Shock Waves** //Pages 385 - 386//__= =shock wave- produced by overlapping spheres that form a cone= =sonic boom - the sharp crack heard when the shock wave that sweeps behind a supersonic aircraft reaches the listeners= Overlapping spheres from a cone produce shock waves. You can only hear a sonic boom when the air craft moves faster than sound. The quick pressure increase causes an explosion due to air expansion. Even if an object is not making sound, if it breaks the sound barrier it WILL create a sonic boom. When you snap a towel or shoot a bullet, you hear the effects of a sonic boom.