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Physics Chap 25 Test
| Question | Answer |
|---|---|
| vibration | a repeating back and forth motion about an equilibrium position |
| what is a vibration like? | a wiggle in time and can happen in one instant |
| wave | a disturbance that is transmitted progressively from one place to the next with no actual transport of matter |
| what is a wave like? | a wiggle in time and space, can't exist in one place |
| what are both forms of energy that move through space as waves? | light and sound |
| what does the period of the pendulum depend on? | the length and acceleration of gravity |
| pendulum | weight (bob) attached to a string that is free to swing |
| what do pendulums do? | swings back and forth with regularity that is used to control the motion of clocks |
| cycle | one complete back and forth swing |
| period | time for one cycle |
| what does period depend on? | does not depend on weight or size of swing, does depend on length of pendulum |
| how do two pendulums compare to each other? | two pendulums of the same length have the same period regardless of mass, a longer pendulum has a longer period |
| what is the source of all waves? | something that vibrates |
| simple harmonic motion | back and forth vibrating motion (oscillation) |
| sine curve | pictorial representation of a wave formed by a swinging pendulum or bouncing spring |
| who first demonstrated a sine curve? | frank oppenheimer |
| crest | high point of the wave |
| trough | low point of a wave |
| amplitude | distance from the midpoint to the crest (or trough) of the wave |
| describe amplitude | the maximum displacement from equilibrium, a measure of the energy of the wave, higher wave has more energy, lower wave has less energy |
| wavelength | the distance from the top of one crest to the top of the next, distance between successive identical parts of the wave, symbol = lambda |
| frequency | the number of vibrations in a given time (usually one second), number of cycles per second, symbol "f" |
| Hertz (Hz) | unit of frequency, 1 cycle per second |
| AM radio | kilohertz |
| FM radio | megahertz |
| frequency of the vibrating source is the frequency of waves | |
| direct relationship | if one variable inceases, the 2nd variable increases (same change) |
| inverse relationship | if one variable increases the 2nd variable decreases (opposite change) |
| how does period relate to frequency? | period of the pendulum is inversely proportional to the frequency, period seconds/cycle, frequency cycles/second, period T, T=1/f, f=1/T |
| how is energy transferred through a wave? | the energy transferred by a wave from a vibrating source to a receiver is carried by a disturbance in a medium, energy is not transferred by matter moving from one place to another within the medium |
| how does the matter move? | up and down while the disturbance moves the energy forward |
| how can you calculate the speed of a wave? | by multiplying the wavelength by the frequency |
| what does the speed of a wave depend on? | the medium through which the wave moves, sound in air=330-350 m/s, sound in water moves 4 times faster |
| how are properties of a wave related? | whatever the medium, speed, frequency, and wavelength are related by formula,wave speed=frequency x wavelength, v-f(lambda) directly related |
| describe the differences between different frequencies | high frequencies: short wavelengths low frequencies: long wavelengths... same speed |
| describe frequency and wavelength in air | in air the product of wavelength and frequency is speed and is the same for every frequency of sound, that is why high notes in a chord are not heard before low notes, the sounds all reach you at the same time |
| how do wavelength and frequency vary? | inversely to produce the same wave speed for all sounds |
| how do you solve a scientific equation? | write GIVEN info(use variable symbol&all #s have unit of measurement), write UNKNOWN(use symbols)write EQUATION in symbols that relate to known&unknown |
| solving equations cont. | substitute #s in equation(including units of measurement) and solve for the unknown, write answer (include units of measurement) |
| what are transverse waves? | the motion of the medium (air, water) is at right angles to the direction of the wave motion (also stadium wave) |
| what are examples of transverse waves? | waves in the stretched strings of musical instruments and the electromagnetic waves that make up radio waves and light are transverse |
| what are longitudinal waves? | the medium moves back and forth in the same direction in which the wave travels (a compression wave) |
| what are some examples of longitudinal waves? | sound waves, springs |
| how can transverse and longitudinal waves be demonstrated? | a loosely coiled spring or slinky, transverse:the end is shaken up and down longitudinal wave is produced |
| when do interference patterns occur? | when waves from different sources arrive at the same point at the same time |
| how do matter and waves differ? | 2 pieces of matter cannot be in the same place at the same time but waves can |
| what is an interference pattern? | a regular arrangement of places where wave effects are increased, decreased or neutralized, caused by overlapping waves |
| what is constructive interference? | crest overlaps crest, reinforcement, result is a wave of increased amplitude |
| what is destructive interference? | crest of one wave overlaps the trough of another, cancellation, result is that the crest of one wave fills in the trough of another, decreased amplitude |
| what are wave patterns of destructive interference? | waves are out of phase (gray stripes) |
| what are wave patterns of constructive interference? | the waves are in phase (light and dark stripes) |
| how do standing waves form? | only if half a wavelength or a multiple of half a wavelength fits exactly into the length of the vibrating medium, when an original wave is reflected back after reaching a rigid surface a standing wave can form |
| how standing waves form cont. | original and reflected waves need to be the same amplitude and wavelength |
| what are standing waves a result of? | interference |
| what is a node? | a result of destructive interference |
| what is an antinode? | a result of constructive interference |
| how do different frequencies affect waves? | different frequencies cause standing wave patterns |
| where are standing waves found? | strings of musical instruments and organ pipes, standing waves can be produced in either transverse or longitudinal waves |
| what is the Doppler effect? | a change in frequency due to the motion of the source of the waves, as a wave source approaches, an observer encounters waves with a higher frequency. as the wave source moves away an observer encounters waves with a lower frequency |
| when are concentric circle waves produced? | when the wave speed is the same in all directions, if something vibrates or bobs at a constant frequency the wavelength will be the same for all successive waves and the wave frequency is the same as the bobbing or vibrating frequency |
| how do observers at different places encounter different wave frequencies? | the same numbers of waves/second are counted by both sides because the source of the wave is stationary, if the bug moves across the water at a speed that is greater than the wave speed the wave pattern is distorted and no longer concentric |
| cont. | different waves/second (frequencies) are counted because the source of the waves is moving, the person who the source is moving towards counts more waves/second(higher freq) because the source is moving toward him |
| cont. | the person the source is moving away from counts fewer waves/second(lower freq) because the source is moving away from |
| does anything else produce the Doppler effect? | sound and light waves also produce the Doppler effect, ambulance coming towards you has a high pitched sound (higher freq) than an ambulance moving away from you (lower freq) low pitched sound |
| how does light have the Doppler effect? | light source moving towards you has a higher frequency (blue shift) light source moving away from you has a lower frequency (red shift), this info tells astronomers how fast stars are spinning how fast galaxies are moving and which way |
| when does a bow wave occur? | when a wave source moves faster than the wave it produces |
| describe bow waves | when the speed of the moving source equals the speed of the waves it produces, the waves pile up at the front edge |
| how do bow waves relate to sound? | a plane travelling at the speed of sound causes the pile up of waves which makes the air "rough" at the front edge the piled up energy is called the sound barrier |
| cont. | when the plane goes past this barrier (supersonic-flying faster than the speed of sound) the plane flies in smooth, undisturbed air |
| what is Mach 1? | flying faster than the speed of sound |
| what is a bow wave? | overlapping edges of wave crests produced when the source is moving faster than the wave it makes, it looks like an overlapping v-shape on the surface of the water, it is made by boats and is 2 dimensional |
| cont. | overlapping at the edges occurs only when the source travels faster than wave speed |
| what is a shock wave? | overlapping edges of spherical wave crests produced when a source is moving faster than the wave, it is a 3D cone shape, the source is moving through the medium such as air, the cone spread out until it reaches the ground |
| when does a shock wave occur? | when an object moves faster than the speed of sound |
| what is a sonic boom? | conical shell of compressed air that sweeps behind a supersonic object reaches the listener's ears, all the crests of sound waves reach the listener at once, this high pressure air sounds like an explosion |
| what else produces a sonic boom? | we dont hear a sonic boom from a subsonic aircraft because the sound wave crests reach our ears one at a time and are perceived as a continuous tone, only when the craft moves faster than sound do the crests overlap and encounter the listener all at once |
| when does a sonic boom occur? | a sonic boom does not just happen once when a plane goes past the sound barrier, the cone of air keeps behind the plane as it moves reaching more listeners on the ground as it flies past |
Created by:
distler
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