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hey rc

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maihuna Legendary Member Default Avatar
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hey rc

Post Sun Sep 13, 2009 5:30 am
Elapsed Time: 00:00
  • Lap #[LAPCOUNT] ([LAPTIME])
    In 1975 Chinese survey teams
    remeasured Mount Everest, the highest
    of the Himalayan mountains. Like the
    Line British in 1852, they used the age-old
    (5) technique of “carrying in” sea level:
    surveyors marched inland from the
    coast for thousands of miles, stopping
    at increments of as little as a few feet
    to measure their elevation, and mark-
    (10) ing each increment with two poles.
    To measure the difference in elevation
    between poles, surveyors used an
    optical level-a telescope on a level
    base-placed halfway between the
    (15) poles. They sighted each pole, reading
    off measurements that were then
    used to calculate the change in elevation
    over each increment. In sight of
    the peaks the used theodolites-
    (20) telescopes for measuring vertical and
    horizontal angles-to determine the
    elevation of the summit.
    The Chinese, however, made
    efforts to correct for the errors that
    (25) had plagued the British. One source
    of error is refraction, the bending of
    light beams as they pass through air
    layers of different temperature and
    pressure. Because light traveling.
    (30) down from a summit passes through
    many such layers, a surveyor could
    sight a mirage rather than the peak
    itself. To reduce refraction errors, the
    Chinese team carried in sea level to
    (35) within five to twelve miles of Everest’s
    summit, decreasing the amount of air
    that light passed through on its way to
    their theodolites. The Chinese also
    launched weather balloons near their
    (40) theodolites to measure atmospheric
    temperature and pressure changes
    to better estimate refraction errors.
    Another hurdle is the peak’s shape.
    When surveyors sight the summit.
    (45) there is a risk they might not all
    measure the same point. In 1975
    the Chinese installed the first survey
    beacon on Everest, a red reflector
    visible through a theodolite for ten
    (50) miles, as a reference point. One
    more source of error is the unevenness
    of sea level. The British
    assumed that carrying in sea level
    would extend an imaginary line from
    (55) the shore along Earth’s curve to a
    point beneath the Himalaya. In
    reality, sea level varies according
    to the irregular interior of the planet.
    The Chinese used a gravity meter to
    correct for local deviations in sea level.
    -------------------------------------------------------------------------------------------------------
    Q32
    It can be inferred from the passage that
    refraction would be most likely to cause
    errors in measurements of a mountain’s
    elevation under which of the following
    conditions?
    A. When there are local variations in sea
    level
    B. When light passes through humid air
    C. When theodolites are used relatively far
    from the mountain peak.
    D. When weather balloons indicate low air
    temperature and pressure.
    E. When sea level has been carried in to
    Within five to twelve miles of the summit.

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    sanp_l Master | Next Rank: 500 Posts Default Avatar
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    Post Sun Sep 13, 2009 1:16 pm
    I feel Option D as an answer is direct.
    Whats the OA?

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    kiennguyen Senior | Next Rank: 100 Posts Default Avatar
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    Post Wed Nov 04, 2009 11:40 pm
    IMO B

    tanviet Legendary Member Default Avatar
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    Post Mon Jan 11, 2010 9:10 pm
    IMO C. I infer from " within 5 to 12 miles of thorodoir"

    this is hard

    bln123 Senior | Next Rank: 100 Posts Default Avatar
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    Post Tue Jan 12, 2010 2:07 am
    My opinion is C

    A -> not an issue
    B -> type of air that would cause disturbance is not mentioned
    D -> see B
    E -> confuses info (see C)

    C -> "To reduce refraction errors, the Chinese team carried in sea level to within five to twelve miles..." so they needed to get close to get a good measurement

    raisethebar Senior | Next Rank: 100 Posts Default Avatar
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    Post Thu Jan 21, 2010 4:27 am
    IMO C.
    plz provide OA

    Post Thu Jan 28, 2010 10:39 pm
    C for me too...

    gmatmachoman Legendary Member Default Avatar
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    Post Fri Jan 29, 2010 2:14 am
    bln123 wrote:
    My opinion is C

    A -> not an issue
    B -> type of air that would cause disturbance is not mentioned
    D -> see B
    E -> confuses info (see C)

    C -> "To reduce refraction errors, the Chinese team carried in sea level to within five to twelve miles..." so they needed to get close to get a good measurement
    Fantastic inference bro
    !!

    IMO C

    Maihuna is not there on the forum ...so OA may not be available..But my guess is C....

    bhavesh_09 Junior | Next Rank: 30 Posts Default Avatar
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    Post Fri Jan 29, 2010 11:12 am
    It should be B

    ajith Legendary Member
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    Post Fri Jan 29, 2010 1:09 pm
    maihuna wrote:
    Q32
    It can be inferred from the passage that
    refraction would be most likely to cause
    errors in measurements of a mountain’s
    elevation under which of the following
    conditions?
    A. When there are local variations in sea
    level
    B. When light passes through humid air
    C. When theodolites are used relatively far
    from the mountain peak.
    D. When weather balloons indicate low air
    temperature and pressure.
    E. When sea level has been carried in to
    Within five to twelve miles of the summit.
    IMO C

    refraction, the bending of light beams as they pass through air layers of different temperature and pressure
    As the distance increases variation in pressure and temperature increases

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    ballubalraj Senior | Next Rank: 100 Posts
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    Post Mon Feb 15, 2010 7:15 pm
    I will go with 'C'

    To reduce the refration error, Chinese used their theodolites closer to the mountain. Hence, the error is more likely when the theodolites are far.

    surfer123 Junior | Next Rank: 30 Posts Default Avatar
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    Post Tue Nov 23, 2010 3:14 pm
    I think it is c too. Where is this question from?

    mundasingh123 Legendary Member Default Avatar
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    Post Tue Nov 23, 2010 10:04 pm
    ballubalraj wrote:
    I will go with 'C'

    To reduce the refration error, Chinese used their theodolites closer to the mountain. Hence, the error is more likely when the theodolites are far.
    Chinese team carried in sea level to
    (35) within five to twelve miles of Everest’s
    summit, decreasing the amount of air
    that light passed through on its way to
    their theodolites. The Chinese also
    launched weather balloons near their
    The telescopes were not brought closer to the peak, the sea level is brought closer.
    Refraction occurs when light passes though different layers of air having different temperatures and pressures.
    When light passes though humid air, temperature and pressure changes

    frank1 Legendary Member Default Avatar
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    Post Thu Nov 25, 2010 3:41 am
    Well
    Down to B and C
    I think B is what manhattan calls 'one word wrong'
    I think word humid is nowhere in passage...
    We will be using our external knowledge of subject if we think humid air has higher density and all....

    and with c
    down from a summit passes through many such layers


    Larger distance means more layers...and higher chances of refrac errors
    more over
    what they do to correct them
    make closer points...

    so C sounds logical from most angles.

    thanks

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    mundasingh123 Legendary Member Default Avatar
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    Post Thu Nov 25, 2010 3:53 am
    frank1 wrote:
    Well
    Down to B and C
    I think B is what manhattan calls 'one word wrong'
    I think word humid is nowhere in passage...
    We will be using our external knowledge of subject if we think humid air has higher density and all....

    and with c
    down from a summit passes through many such layers


    Larger distance means more layers...and higher chances of refrac errors
    more over
    what they do to correct them
    make closer points...

    so C sounds logical from most angles.

    thanks
    Farther distance from the peak means more layers of air (with different temperature and pressure or same temperature and pressure ) ? we need to clarify this.When its already mentioned that refraction takes place due to temperature and pressure change , we know that humid air means temperature and pressure change .This makes use of info given in passage itself and no outside knowledge , does it?

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