final exam

Question 1

do we hear the same frequency that is emitted when nothing moves?

Answer 1

yes

Question 2

how can the intensity be defined?

Answer 2

• power/perpendicular are
• variation of pressure compared to 1 atm

Question 3

what are sound waves?

Answer 3

• longitudinal waves
• diplace air

Question 4

how does the density and rigidity affect the v?

Answer 4

• more rigid = v higher
• more dense = v lower

Question 5

what are waves of pressure?

Answer 5

medium compressed and expands

Question 6

what can you change to change a note of an instrument (to change f)?

Answer 6

• tension (higher T = higher f)
• mass/length (mu) (higher mu = lower f)
• length (smaller length = higher f)

Question 7

what are standing waves?

Answer 7

• supposition of two harmonic waves with same A,w,k but opposite directions of travel (different sign before w)
• y tot (x,t) = 2Asin(kx)cos(wt)
• only move up/down

Question 8

what is completely destructive interference?

Answer 8

when the phase difference between the two = odd multiple of pi (y1 and y2 cancel)

Question 9

what does it mean when waves are out of phase?

Answer 9

same A, w, k, but different phase constant

Question 10

what is the reflection when there is the junction of 2 strings?

Answer 10

• partial reflection and partial transmission
• smaller A than original

Question 11

what is the reflection of a wave on a string with a vertically free end?

Answer 11

the reflected wave is inverted left/right but NOT up/down

Question 12

what is the reflection of a wave on a string with a fixed end?

Answer 12

reflected pulse is inverted up/down and left/right

Question 13

what happens after any interference of 2 waves?

Answer 13

they pass through one another unaffected

Question 14

what is distructive interference?

Answer 14

y1 and y2 have opposite signs (one is up side up and other is upside down) = smaller wave (like subtraction)

Question 15

what is constructive interference?

Answer 15

y1 and y2 have the same sign (so same side up/down) = they reinfore

Question 16

what to do when asked the formula when the wave moves only to right or only to left?

Answer 16

use y = f(x-vt) + g(x+vt)

Question 17

what to do when asked a velocity at specific t or specific x or both?

Answer 17

partial derivative of y with relation to t

Question 18

what are transverse waves and examples?

Answer 18

• motion of medium is perpendicular to propagation of wave
• waves on a string, ripples on water, seismic S waves

Question 19

what are longitudinal waves and examples?

Answer 19

• motion of medium is parallel to propagation
• sound waves, compressed spring, seismic P waves

Question 20

give the waves in order of increasing frequency.

Answer 20

smallest:
long waves (10^4)
radio waves (10^11)
microwaves (10^12)
infrared (10^14)
visible spectrum (10^15)
ultraviolet (10^17)
X rays (10^20)
gamma rays

Question 21

give the waves in order of increasing wavelength.

Answer 21

gamma rays (10^-13)
X rays
ultraviolet
visible spectrum
infreared
microwaves
radio waves
long waves

Question 22

give the order of increasing wavelength for the visible spectrum.

Answer 22

violent (400 nm)
blue (450 nm)
green (550 nm)
yellow (550-600 nm)
orange (600 nm)
red (600-700)

Question 23

how do E and B travel in a vacuum?

Answer 23

like electromagnetic waves

Question 24

do EM waves contain both E and B?

Answer 24

yes, and they are independent

Question 25

how are plane harmonic EM waves polarized?

Answer 25

linearly polarized

Question 26

what are plane waves and why are they called that?

Answer 26

- EM waves are in 3D space (not along a line) - at a given t: E and B are constant for all points with the same x (creates a plane of field at that x) - every point that has the same x (no matter y, z) have the same electric field

Question 27

what type of waves are EM waves?

Answer 27

transverse waves, since E and B are perpendicular to the propagation of the wave

Question 28

how to tell the direction of polarization?

Answer 28

direction of the oscillation for E

Question 29

what are the possible components for E in plane EM waves?

Answer 29

y and z, since propagation along x, no x component

Question 30

in spherical waves, is the amplitude of Em constant?

Answer 30

no, because the amplitude decreases as the distance becomes greater (when farther away)

Question 31

at a large distance, spherical waves fronts become like what?

Answer 31

like plane waves

Question 32

in linearly polarized EM waves, what is the direction of propagation?

Answer 32

direction of oscillation of E (NOT B)

Question 33

in a mass spring system, when is the velocity at its max? when is it 0?

Answer 33

max: center, when x = 0 0: when x = A (x is at its max)

Question 34

what is the type of force of the spring force?

Answer 34

restoring force (points toward origin)

Question 35

does the total mechanical energy oscillate as a function of time in a mass spring system?

Answer 35

no

Question 36

does T depend on the position of the block?

Answer 36

no

Question 37

if an oscillation of a mass spring system gives a period T when started at x=D, will T increase, decrease or stay the same if it is kicked?

Answer 37

stay the same, since w(res) = w

Question 38

in a velocity vs time graph, where is the point where x is at its max? when is it at 0?

Answer 38

max: when v=0 0: when v at max

Question 39

how does the potential energy oscillate (as fct of time) in relation to the position?

Answer 39

twice as fast, only in the positive

Question 40

is the period the same in a vertical and horizontal mass spring system (same mass and spring)?

Answer 40

yes

Question 41

what is the steady state of the motion in a forced harmonic oscillation?

Answer 41

motion becomes stable with constant amplitude at the frequency of the driving force

Question 42

what is a longitudinal wave?

Answer 42

a wave for which the oscillation of matter is parallel to the direction of propagation

Question 43

what is needed to get a standing wave?

Answer 43

two waves travelling in opposite directions, have no phase difference or one of pi

Question 44

if two harmonic waves travel in the same amplitude, wavelength and frequency on the same string, in what case would they cancel completely everywhere at all time?

Answer 44

if the waves travel in the same direction and have a phase difference of of pi

Question 45

what happens to two waves travelling in opposite direction on the same string?

Answer 45

they will pass through each other unaffected

Question 46

what does i dot i give (or j dot j, k dot k)?

Answer 46

1 (i dot j = 0)

Question 47

what does i cross i give?

Answer 47

0 (need to cross different vectors to get value)

Question 48

which of maxwell's equations are a flux/volume?

Answer 48

- del dot E - del dot B

Question 49

which of maxwell's equations are a line intergral/area?

Answer 49

- del cross B - del cross E

Question 50

which maxwell equation is about the line integral per area of the magnetic field around a point?

Answer 50

3rd one (del cross B = line integral of B)

Question 51

do all electromagnetic waves in a vacuum contain a E ad B?

Answer 51

yes

Question 52

do E and B carry different amounts of energy in an electromagnetic wave in a vacuum?

Answer 52

no, they carry the same amount of energy

Question 53

are the E and B parallel in an EM wave in a vacuum?

Answer 53

no, they're perpendicular

Question 54

is the frequency, wavelength and light speed the same in a medium vs in air?

Answer 54

frequency; yes wavelength; no speed; no

Question 55

in a medium, are maxima closer together?

Answer 55

yes (smaller wavelength)

Question 56

is light speed bigger or smaller in a medium?

Answer 56

smaller

Question 57

what type of function is a shm (position vs time)?

Answer 57

sinusoidal function

Question 58

does the total mechanical energy of an shm vary in time?

Answer 58

no, it's constant

Question 59

does the period of an shm depend on the amplitude?

Answer 59

no

Question 60

what type of waves are sound waves ?

Answer 60

longitudinal

Question 61

what is needed for something to create a shock wave in the air?

Answer 61

the speed of the object moving must be faster than the speed of sound (343 m/s)

Question 62

what are the three conditions in order that two light sources produce a stable interference pattern?

Answer 62

1. must emit light at the same frequency 2. must emit light with same direction of polarization 3. at any point on screen, phase difference from the two must remain constant

Question 63

what happens to the intensity pattern when light is sent on 2 slits and more slits are added?

Answer 63

- width of the strong maxima will decrease - weak maxima will appear between strong maxima - strong max will remain in the same location

Question 64

what does the intensity pattern of a grating look like?

Answer 64

very very sharp peaks with very small secondary max

Question 65

what is rayleigh's criterion for two stars to be barely resolved?

Answer 65

- the cneter of the second star falls on the first min of the first star - very very close and center overlaps, but not completely superimposed

Question 66

what is diffraction?

Answer 66

superposition of waves from an infinite number of point sources inside the aperture

Question 67

is diffraction noticeable in a 2 slit experiment where the slits have negligeable width?

Answer 67

no, the maxima are always at the same intensity