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MCAT PHYSICS > Lect 6: Waves > Flashcards

Lect 6: Waves Flashcards

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1
Q

the transfer of momentum and energy from one point to another
3 types: mechanical, electromagnetic, and matter

A

wave

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2
Q

type of wave that obeys laws of physics

need to travel through a medium

A

mechanical wave

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3
Q

type of medium that is perfectly elastic; wave maintains its shape; does not disperse
i.e. Ideal waves
ALL materials on the MCAT

A

nondispersive medium

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4
Q

2 types of mechanical waves

A

transverse

longitudinal

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5
Q

type of mechanical wave where the medium is displaced perpendicularly to the wave
i.e. waves on a string

A

transverse wave

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6
Q

type of mechanical wave where the medium is displaced parallel to the wave
i.e. sound waves

A

longitudinal wave

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7
Q

measured from any point on a wave to the point where the wave repeats itself (i.e. peak to peak / trough to trough)
x-axis = displacement of the wave
SI unit = meters

A

wavelength (lambda)

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8
Q

the number of wavelengths that pass a fixed point in one second
(cycles / second)
SI Unit = Hertz or 1 / sec

A

frequency (f)

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9
Q

Equation: Wave velocity

*Dictated by MEDIUM

A

V(wave) = frequency * wavelength

Note: MEDIUM dictates wave velocity, not the frequency or the wavelength

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10
Q

reciprocal of frequency
number of seconds it takes for one wavelength to pass a certain point
(seconds / cycle)

A

period (T)

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11
Q

Equation: Period

A

Period (T) = 1 / f

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12
Q

a wave’s maximum displacement from 0

always positive

A

Amplitude (A)

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13
Q

A wave function is always plotted against either ______ or _____

A

displacement or time

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14
Q

A medium’s _____ and _____ affect the velocity of a wave

A

elasticity (∆ shape)

inertia (∆ motion)

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15
Q

an object’s tendency to resist motion

inversely proportional to velocity

A

Intertia

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16
Q

For a gas, velocity ______ with temperate

A

increases

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17
Q

Waves (speed up / slow down) through a heavy medium

A

slow down

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18
Q

Waves (speed up / slow down) through a stiff medium

A

speed up

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19
Q 
defines Power (rate at which a wave transfers Energy)
increases w/ the SQUARE of the AMPLITUDE and SQUARE of the FREQUENCY
SI unit = W / m^2
A

Intensity (I)

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20
Q

The wave source determine’s a wave’s _____ and ______.

A

Amplitude & Frequency

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21
Q

The medium through which a wave travels determines _____ and ______

A

Density and velocity

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22
Q

artificial scale to describe intensities

SI unit = Decibel (dB)

A

Intensity level (b)

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23
Q

If Intensity increases by a factor of 10, the decibels increase by ______

A

10 decibels

24
Q

If Intensity increases by a factor of 100, the decibels increase by ______

A

20 decibels

25
Q

If I add 1 zero to intensity, I add _____ decibels

A

10 decibels

26
Q

relates wavelength, frequency, place, and time or origin
represented by a horizontal shift on a graph
each wave represents 360º

A

phase of a wave

27
Q

two waves of the same WAVELENGTH that begin at the same point

A

“in phase”

28
Q

waves that are transverse and occupy the same space

add displacements at each point along the wave to form a new wave

A

Interference

29
Q

the sume of the displacements of two waves creates a larger displacement

A

constructive interference

30
Q

the sum of the displacements of two waves results in a smaller net displacement

A

destructive interference

31
Q

occurs when 2 waves with slightly different FREQUENCIES are superimposed
will experience BOTH constructive and destructive interference at different points

A

beat

32
Q

difference in the frequency of the original two waves
must = 0 for an instrument in perfect tune
alternates up and down in intensity of the noise

A

beat frequency

33
Q

Equation: Beat frequency:

A

f (beat) = | f1 - f2 |

34
Q

what a tuner hears
frequency creating this = the average of the frequencies from the fork and the instrument
proportional to frequency

A

Pitch

35
Q

the orientation of this waves depends on the density of the two media
denser media: INVERTS wave
less dense medium: wave is turned UP

A

reflected up

36
Q

When a wave transfers from 1 medium to another, ____ changes but _____ stays the same

A

wavelength changes

frequency stays the same

37
Q

the point where two sine waves w/ the same wavelength traveling in opposite directions collide on a perfectly elastic string
does NOT move (x = 0)

A

node

38
Q

points on perfectly elastic string where 2 sine waves w/ equal wavelengths experience the maximum constructive interference

A

antinode

39
Q

a perfectly elastic string holds still at the nodes and moves violently up and down at the antinodes in this type of wave

A

standing wave

40
Q

list of wavelengths from LARGEST to SMALLEST of possible standing waves

A

Harmonics

41
Q

longest wavelength in a harmonic; created w/ the fewest nodes (2)
distance from one medium to another = 1/2 * wavelength

A

Fundamental wavelength / first harmonic

42
Q

created by adding another node between the two media in a harmonic
distance between the two media = wavelength

A

second harmonic / wavelength 2

43
Q

If only one side of a string is tied down or only one end of a pipe is open, the untied or open end is an ______.
*When this happens, all of the even numbered harmonics are missing, and the length of the pipe/string equals the number of harmonics times the wavelength divided by 4

A

antinode

44
Q

If both sides of a string are tied down or both sides of a pipe are open, both sides of the pipe / string are called _____.
*In this case, the length of the pipe/string equals the number of nodes times the wavelength divided by 2

A

nodes

45
Q

causes by a standing wave

to vibrate at a string’s natural frequency

A

resonate

46
Q

a wave’s natural frequency

found for any given harmonic by v = frequency * wavelength

A

resonant frequency

47
Q

condition where the natural frequency and the driving frequency are equal for a wave

A

resonance

48
Q

any motion that repeats itself

A

harmonic motion (periodic motion)

49
Q

a perfect sine wave
specific type of harmonic motion
sinusoidal function in time
objects in this type of motion exhibit similar properties:
-acceleration is directly proportional to the displacement but w/ the OPPOSITE sign
-aceleration and displacement are related by the square of the frequency
-No energy is lost to the surroundings in the oscillation b/w kinetic energy and potential energy
Ex: Pendulum
Ex: Mass bouncing on the end of a massless spring

A

simple harmonic motion

50
Q

simple harmonic motion that switches between kinetic and potential energy
no energy lost to surroundings
Ex: Pendulum

A

oscillation

51
Q

Waves are unaffected by speed of the source
if the sources moves relative to the receiver, each wave travels a different distance and receiver gets them at different frequencies

A

Doppler Effect

52
Q

When teh source and observer get closer to each other (move toward each other) observed frequency ______ and observed wavelength ____

A

observed frequency increases

wavelength decreases

53
Q

Equations: Doppler Effect

A

∆f / f (s) = v / c
∆v / wavelength (s) = v / c
Note: v = speed at which objects approach each other

54
Q

If the light source and the observer approach each other, _____ shortens and shows a blue shift.

A

Wavelength

55
Q

If the light source and the observer move away from each other, wavelength lengthens and shows a ______ shift.

A

Red

56
Q

Objects moving in the same direction at the same speed have no _____ and relative velocity = 0, so ∆f = 0

A

Doppler Effect

MCAT PHYSICS (5 decks)

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