Physics - Waves and Light

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Physics - Waves and Light
2011-05-01 11:12:07

Waves, Light, and Optics
Show Answers:

  1. WAVES
  2. What is a wave?
    transfer of momentum between two points
  3. mechanical waves require what in order to travel?
  4. transverse v. longitudinal wave
    transverse: medium is displaced perpendicularly to direction of wave propagation

    longitudinal: medium is displaced parallel to the direction of wave propagation
  5. sound in air is what kind of wave?
  6. amplitude is always what sign?
  7. velocity of a wave is dictated by?
    medium it's traveling in
  8. what two aspects of the medium affect velocity of the wave?
    • medium's resistance to change in:
    • 1- shape (elasticity)
    • 2- motion (inertia)
  9. greater density medium makes wave travel faster or slower?
  10. heavier medium - faster or slower?
    stiffer medium - faster or slower?
    heaver slow waves down

    stiffer mediums speed waves up
  11. for a gas medium, velocity of the wave changes how with changing temperature?
    velocity increases with temperature
  12. do sound waves move more quickly through hot or cold gases?
  13. elastic and interial components of medium store....
    elastic = potential energy

    interial = stores kinetic energy
  14. wave velocity is independent of...
    frequency, wavelength, and amplitude
  15. surface waves: transverse or longitudinal?
    completely neither
  16. intensity (what is it and units)
    energy transfer per area

  17. intensity increases with the square of?
    amplitude and frequency

    greater (amplitude and frequency)2 = greater intensity
  18. does intensity depend on medium?

    density and velocity
  19. increase area = decrease intensity: snapping fingers example
    propagates waves in all directions

    energy is constant, but area is over a larger sphere

    decrease in intensity of the sound
  20. intensity level measured in....
    decibels (dB)
  21. if intensity increases by a factor of 10, decibels increase by...
    addition of 10 decibels

    adding 2 zeros to intensity = adding 20 decibels
  22. in phase v out of phase
    in phase: same wavelength, start at same point

    out of phase: travel different distances but arrive at same point
  23. constructive v. destructive
    constructive = sum results in greater displacement

    destructive = sum results in smaller displacement
  24. superposition
    any wave can be created by superposition of many sine waves
  25. beat
    occurs when two waves with slightly different frequencies are superimposed
  26. how does beat work?
    some points will be nearly in phase (constructive)

    some points will be out of phase (destructive)
  27. audible beats must have close frequencies?

    in other words, the two frequencies shouldn't be too far aparat
  28. first and second harmonic have a ratio of
  29. beat frequency is equal to:
    fbeat = I f1- f2 I
  30. beat frequency is an alternating increase and decrease in....
    intensity of the noise
  31. pitch correlates to...

    high frequency = high pitch
  32. when a wave transfers from one medium to the next, does wavelength or frequency change?
    frequency remains the same

    wavelength changes
  33. standing waves
    node and antinodes
  34. node
    point of no displacement [in line]
  35. antinode:
    point that experiences maximum constructive interference
  36. what is a harmonic series?
    only certain wavelengths could create a standing wave
  37. 1st harmonic: how many nodes and antinodes? length of rope?
    fundamental wavelength

    one antinode

    length of rope = 1/2(wavelength)
  38. second harmonic
    created by adding another node

    two antinodes

    L = 2/2 (wavelenth) = wavelength
  39. each successive harmonic is create by
    adding another node
  40. equation for length of rope
  41. L = (n × wavelengthn)/2 (n = 1,2,3….)
  42. equation for wavelenghtn
    wavelength = wavelength/n
  43. resonance
    vibrate at is resonant frequency
  44. how can you find resonant frequency?
    velocity through a medium is constant,

    • so when it resonates, its resonant frequency is
    • v = (lambda)(freq.)
  45. what does simple harmonic motion mean?
    it repeats itself
  46. what kind of function is it?
    sinusoidal function of time
  47. example of simple harmonic motion
    standing in front of someone riding a bike: looks like they're peddling up and down

  48. equation for angular frequency
    w = 2pif
  49. in simple harmonic motion, how is acceleration related to distance?
    directly proportional

    but opposite signs
  50. What relates acceleration and frequency?
    square of the frequency
  51. how does mass on pendulum affect motion?
    it doesn't
  52. period for pendulum (equation)
    T = 2pi (L/g)1/2
  53. when pendulum is in the middle (straight down) KE and PE are
    KE is at its maximum

    PE is at its minimum
  54. what kind of curve is the KE of a pendulum?
    sine curve

    (simple harmonic motion)
  55. Hooke's law: mass hanging from a spring:

    forces are greatest when? acceleration is constant?
    forces are greatest when spring is fully compressed or fully extended

    since F = ma, and a is also greatest

    [Hooke's law: F=-k x change in x
  56. period (T) in simple harmonic motion
    T = (2pi) x sq.rt.(m/k)

  57. energy oscillates between...
    KE and one or more forms of potential energy
  58. LIGHT
  59. What is an electromagnetic wave?
    traveling oscillation of an electric and magnetic field
  60. What kind of wave is what kind of wave?
    transverse wave
  61. How are electromagnetic fields generate?
    acceleration of an electric charge
  62. electromagnetic spectrum: energy and wavelength
    inversely proportional:

    E = hf = h(v/lambda)
  63. electromagnetic spectrum (left to right) inc. or dec. wavelength and frequency
    left to right - dec. wavelength, inc. frequency

    so moving left to right = increasing energy
  64. order of increasing energy
    radio < microwaves < IR < ROYGBIV < UV rays < x rays < gamma rays
  65. intensity of light is a measure of...
    frequency of photons (photon energy stays the same)
  66. what is monochromatic light?
    light with a single frequency
  67. index of refraction (equation)
    n = c/v

    • c = 3 x 108
    • v = speed of light in medium
  68. light waves travel faster or slower when propagating through a medium

    • index of refraction for air = 1
    • other medium = greater than 1
  69. light made of photons:
    what is the electromagnetic wave?
    each photon = electromagnetic wave
  70. dual nature of light - what do each reflect?
    wave = propagation properties

    particle = energy transformation
  71. angle of refraction (equation)
    n1sin1 = n2sin2
  72. light's preferred path
    shortest path possible
  73. when light crosses into a new medium, what happens to frequency and wavelength?
    frequency stays the same

    wavelength changes
  74. how does wavelength change, increase or decrease?
    n2 is greater = wavelength decreases

    n2 is less = wavelength increases

    (inversely proportional)
  75. energy of a photon
    E = hf

    h = 6.63 x 10-34
  76. when light is refracted, while it still have the same amount of energy per photon?

    just that some photons were reflected and others refracted
  77. critical angle: what is it, and what is the equation?
    all photons are reflected (none refracted)

  78. What is dispersion of light?
    different light frequencies travel at slightly different speeds

    (index of refraction varies with frequency)
  79. Do longer waves or shorter waves move faster?
    longer waves - lower frequency
  80. since longer waves move faster, is there a greater or lesser bending at the media interference?
    less dramatic
  81. What is diffraction?
    when a wave moves through a small opening, it bends around the corners of it

    bending = diffraction
  82. size of opening, relative to wavelength of the wave - and how will that affect bending of the wave
    the smaller the hole, the greater the spreading of light

    so, small opening = long wavelength = more bending
  83. what happens when diffracted waves meet?

    forms bright and dark images
  84. which produces bright and which dark images?
    constructive = bright

    destructive = dark
  85. diffraction is part of light's wave or particle phenomenon?
  86. If light were purely a particle, what would happen when it moved through the slit?
    no diffraction

    all light would go directly to detector at the level of the slit.
  87. mirrors and lenses: which reflect and which refract?
    mirrors = reflect

    lenses = refract
  88. lenses: diverging and convergine (relative to mirror concave and convex)
    diverging = concave

    converging = convex

    Thicker Center Converges
  89. radius of curvature:
    decrease radius of curvature is...
    a sharper curve

    straighter line = larger radius of curvature
  90. what is the focal length?
    focal point is separated from mirror/lens by the focal length (f)
  91. focal length of mirror
    1/2 radius
  92. focal length of lens - affected by:
    • refractive index of lens (n1)
    • substance around the lens (n2)
    • radii of curvature
  93. what is the magnification
    ratio of size of image/object

  94. magnification (equation)
    m = - (di/do) = (hi/ho)
  95. what does negative in the magnification equation mean?
    if both distance are positive, image is inverted
  96. positive magnification means
    negative magnification means
    positive = upright image

    negative = inverted image
  97. thin lens equation:
    1/f = (1/do) + (1/di)
  98. System for Mirrors and Lenses
    1. I (eye) am positive that real is inverted
  99. images on side of "eye" are always....
    images on the other side are always...
    side of eye = positive, real, and inverted

    other side = negative, virtual, and upright
  100. front and back for mirror and lens
    eye is in front of mirror

    behind lense
  101. front and back - positive and negative
    front = positive

    behind = negative
  102. What are negative, virtual and upright?
    • convex mirrors
    • diverging lenses
  103. what are positive, real, and invert?
    • concave mirrors
    • converging lens
  104. exception:
    if object is within focal distance os concave mirror or converging lens: image is negative, virtual, upright
  105. so, what is always negative
    convex mirror, diverging lens
  106. Power of lens (equation)
    (1/f) = (1/di) + (1/do)