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physics ch. 25
Question | Answer |
---|---|
what is a vibration? | a repeating back and forth motion about an equilibrium position |
what is a wave? | a disturbance that is transmitted progressively from one place to the next with no actual transport of matter |
what are 2 forms of energy that move through space as waves? | light and sound |
what is a pendulum? | weight attached to a string that is free to swing |
what is a cycle? | one complete back and forth swing |
what is a period? | time for one cycle |
what does the period depend on? | length of the pendulum |
what does the period not depend on? | weight or the size of the swing |
what do two pendulums of the same length have? | have the same period regardless of the mass |
If the pendulum is longer what happens to the period? | longer |
what does a longer pendulum do? | swings back and forth more slowly |
what is a simple harmonic motion? | back and forth vibrating motion |
what is a sine curve? | pictorial representation of a wave formed by swinging pendulum or bouncing swing. |
what are the high points on a wave called? | crests |
what are the low points on a wave called? | troughs |
what is amplitude? | the distance from the midpoint to the crest or trough of the wave |
what is the maximum displacement from equilibrium? | amplitude |
what does the amplitude do? | 1. Measures the energy of the wave 2. higher wave has more energy 3. lower wave has less energy |
what is wavelength of a wave? | the distance from the top of one crest to the top of the next one. |
what is frequency? | number of vibrations in a given time and the number of cycles per second |
what is the symbol for frequency? | f |
What happens if a vibration occurs in one second? | the frequency is one cycle per second. |
what happens if two vibrations occur in one second? | the frequency is two cycles per second |
What is the source of all waves? | something that vibrates |
what is the frequency of the vibration also the frequency for? | waves |
what is the period of the pendulum inversely proportional to? | frequency |
what is the inverse of the frequency? | period. |
what is the symbol for period? | T |
How is the energy transferred in a wave from a vibrating source to a receiver? | carried by a disturbance in a medium |
when is there no transfer of matter in a wave from one place to another? | when energy is transferred by a wave |
what way does matter move? | up and down |
what does the disturbance move? | the energy forward |
what is the water, air, and string through which wave energy travels? | medium |
how is energy not transferred? | by matter moving from one place to another withing the medium |
what does the speed of a wave depend on? | the medium through which the wave moves. |
why do wavelength and frequency vary inversely? | to produce the same wave speed for all |
what do low frequencies have? | long wavelength |
what do high frequencies have? | short wavelength |
In transverse waves- where is the motion of the medium compared to the direction of the wave motion? | right angle |
In longitudinal waves where does the medium move if it is in the same direction in which the wave travels? | back and forth |
What is another word for a longitudinal wave? | a compression wave |
what is an example of a compression wave? | a sound wave, spring |
How is a way that both transverse and longitudinal waves can be demonstrated? | a loosely coiled spring |
What wave is produced when the end of a coiled spring is shaken up and down? | transverse |
What wave is produced when a coiled spring is shaken in an out? | longitudinal wave is produced |
what 2 pieces cannot be in the same place at the same time? | matter |
what 2 pieces can be in the same place at the same time? | waves |
An interference pattern is a regular arrangement of places where wave effects are increased, decreased, or neutralize. What is this caused by? | overlapping waves |
what happens in constructive interference? | crest overlaps crest |
What is the result of the reinforcement? | a wave of increased amplitude |
What is destructive interference? | crest of one wave overlaps the trough of another |
What is the result of cancellation? | The result is that the crest of one wave fills in the trough of another. |
What kind of amplitude is destructive interference? | decreased amplitude |
In what interference are the waves out of phase? | destructive |
In what interference are the waves in phase? | constructive |
What are some characteristics of interference? | all wave motion, whether the waves are water waves, sound waves, or light waves |
When can a standing wave form? | When an original wave is reflected back after reaching a rigid surface a standing wave can form. |
What do the original and reflected waves need to be? | the same amplitude and wavelength |
What are standing waves a result of? | interference |
What interference is a node? | destructive |
what interference is an antinode? | constructive |
What do different frequencies cause? | different standing wave patterns. |
What are standing waves found in? | strings of musical instruments, organ pipes |
where can standing waves be produced? | transverse or longitudinal waves |
What is the Doppler Effect? | change in frequency due to the motion of the source of the waves |
what happened if the wave it make is concentric circles? | the wave speed is the same in all directions |
What happens if a bug bobs in the water at a constant frequency? | the wavelength will be the same for all successive waves and the wave frequency is the same as the bug's bobbing frequency. |
If two people count the same number of waves per second the source has to be what? | stationary |
If two people count different numbers of waves per second the source has to be what? | moving |
If your counting more waves per second why is the frequency higher? | the source is moving towards him |
If your counting less waves per second why is the frequency lower? | source is moving away from him |
What also produces the Doppler Effect? | sound and light |
If a light source is moving towards you does it have a high or low frequency? | high |
if it is a high frequency what kind of shift is it? | blue shift |
If a light source is moving away from you does it have a low frequency or high? | low |
If it is a low frequency what kind of shift does it have? | red shift |
What is "piled up energy" called? | sound barrier |
If a plane traveling at the speed of sound causes the pile up of waves what does it make the air like at the front edge? | rough |
when a plane goes past this "sound barrier" what happens? | it is supersonic |
What is an airplane flying at the speed of sound? | mach 1 |
What are bow waves? | overlapping edges of wave crests produced when the source is moving faster than the wave it makes |
What happens when the source moves faster? | the V shape becomes narrower |
What is a shock wave? | overlapping edges of spherical wave crests produced when a source is moving faster than the wave. |
What does the cone look like? | 3-Dimensional |
what is a sonic boom? | conical shell of compressed air that sweeps behind a supersonic object reaches the listener's ears |
Do all the crests of sound waves reach the listener at once? | yes |
What does the high air pressure sound like? | explosion |
What don't we hear from a subsonic craft? | sonic boom |
When do the crests overlap? | Only when the craft moves faster than sound |
Does a sonic boom happen once when a plane goes past the sound barrier? | no |
When the plane is flying what does the cone of air do? | keeps behind the plane reaching more listeners on the ground as it flies past |