Test 1 Concepts Flashcards
If a wave moves along a slinky at a velocity of 4m/s, how far does a single coil move in 5 seconds?
Can’t tell - because the speed at which the wave propagates does not equal the speed of displacement of a single coil (that depends on amplitude and frequency.)
V=50m/s, A=2m, w=4m. How much time does it take for a particle on the transverse wave to move 20m?
0.2 seconds.
Find distance traveled in one cycle, then how many cycles necessary, then multiply by period (w/v).
If a guitar string is sixteen times as thick as a thinner string, what is the effect on the speed of the waves when its plucked?
The speed is 1/4 of the thinner string. This is because the velocity is the square root of Ft/m. sr of 1/16 is 1/4.
What does the velocity of a wave depend on?
Springyness/density a more dense item will have a lower velocity and frequency.
What happens to the intensity of a sound if the radius is doubled?
intensity drops by a factor of four. –> 1/2^2 =1/4
What is the unique characteristic of the intensity of a plain wavefront?
intensity is constant (laser beam.) because the beam does not spread out (no change in area.)
What is a wavefront?
a surface connecting all points of equal amplitude.
What happens to the amplitude of a sound when it is spread over a larger area?
the amplitude drops because the same amount of power is spread over a large area.
What aspect of a sound wave is perceived as the pitch?
the frequency. this is why pitch stays the same in different mediums.
If a source of sound is moving away from an observer, what is the affect on the pitch?
it decreases
If a source of sound is moving towards an observer, what is the affect on the pitch?
it increases
What happens if two waves come together at the same place?
their amplitudes add together
What happens to the sound of two superimposed sources of the same frequency if they are in different places in the same room?
Interference due to path difference. the observed sound fluctuates as the sound waves line up in different ways (constructive/deconstructive.)
What happens when two sound sources of different frequencies are in the same room?
Interference - the intensities add and a uniform sound distribution is observed.
What properties of a wave lead to standing waves that exhibit interference between the source and reflections of the wave?
the length of the wave is an integral number of 1/2 wavelengths. L=wave/2, wave, 3wave/2. with nodes at either end.
What type of pipe has only odd harmonics?
a pipe that is open at one end, closed at the other.
How are instruments tuned?
a tuning fork produces the desires frequency, and the note is adjusted on the instrument until there is no perceptible beat present.
how are electromagnetic waves created?
by a cycle of changing E fields and Changing B fields. (ex moving a charge up and down on an antenna, hydroelectric dams.)
An E-field velocity of fields (speed of light), and a B-field are always ____ to one another
perpendicular
What happens happens to the observed sound if two sound waves of the same frequency pass through the same place at the same time?
the intensity of the sounds varies as the sound waves exhibit interference due to different paths. the sound changes as the waves line up in different ways.
as you move away from an object emitting sound, what happens to the observed frequency?
the observed frequency is less than the source frequency
If you move twice as close to a sound source, what is the effect on the intensity?
intensity is increased by a factor of four. this is because I is proportional to 1/r^2. the same amount of power is divided by an area four times smaller.
What sound variable stays the same when a guitar string is tightened?
the wavelength. because the length of the string is fixed and wavelength=2L.
