Comments on grading
of the midterm 1 essay questions
Why didn't you
score 20 on the midterm? Mabye
because we were unfair. But it is
also possible that you didn't really earn 20 points.
James has gone
to the trouble of trying to express what it took to earn points on the midterm
exam. If you would like to do
better, study the following. It
has three parts:
A. General
comments that apply to all essays.
B. Satellites.
Specific ideas that he was looking for.
C. Radioactivity. Specific ideas that he was looking for.
The goal of the
essay was to explain to a intelligent and informed skeptic the topic of the
essay. In grading the essay, the
following things were influential:
1.
Comprehensive information about the subject communicated clearly. I was looking
for all the information that in the course on the subject. It wasn't enough to
write a cryptic sentence referring to the Linear Hypothesis. You need to explain it in a way that
informs the uninformed reader.
Wrong information significantly hurt the grade; it casts doubt on even
the correct facts.
2. Ease of
reading and presentation. Coherent
grammar was beneficial. Paragraphs are a good way to organize your essay into
distinct parts. Legible handwriting also helps. Run on or awkward sentences
detract from the presentation. Weird constructions that require arrows to
direct me from one sentence or paragraph to another were mostly ignored, as was
writing which curled around corners up the margin. Good organization of the essay keeps the information flowing
naturally and transitions between subjects smooth.
3.
Brevity. As I stressed in the
review session, for the same information, writing less is better. Unnecessary and filler sentences
detract from the essay. Excessive
introductions or conclusions are excessive. Concise and clear explanations are ideal.
I didn't take a
set amount of points off for each mistake. Instead, I read the entire essay, and graded on the overall
impression it made. Essays that were a joy to read and informative got a
20. The harder it was to read, and
the less informative it was, the lower grade it recieved.
The three
orbits (Low-Earth, Medium-Earth, and Geosynchronous), with their altitudes,
orbital periods, and types of satellites in each.
The
impossibility of putting a spy satellite over Iraq. First due to its altitude, and the impossibility of
currently-sized telescopes/cameras from taking detailed pictures (stating a
100-meter resolution is a plus).
The second due to the requirement that Geosynchronous satellites need to
be other the equator (and why), which makes it impossible for them to be over
Iraq (which isn't on the equator).
Relating the orbital period of a LEO to the fact that the satellite will
only be near the target location for about 7.5 minutes, necessitating multiple
satellites and allowing people to conceal activities during those windows.
Lastly, some
mention of drones or spy planes, noting that they can be shot down.
The most
critical part is the direct danger of radiation. The levels of exposure and corresponding levels of radiation
sickness. A decent explanation of
the Linear Hypothesis and preferrably an example. Statements about why we
expect the Linear Hypothesis to hold are a plus.
A description
of what radiation and radioactivity are, types of radioactivity, and what a rem
is.
Radiation doses
from the environmental background, ourselves, and x-rays. Exposure from living
near a nuclear power plant a plus.
Overall rates of cancer, and importantly relating these data to compare
risks.
The effects of
Chernobyl and Three-Mile Island.
The impossibility of a nuclear power plant exploding like a nuclear bomb
and the general power plant safeguards.
Nuclear waste and its dangers, including groundwater contamination.
Except for the
first paragraph, these are optional.
No essay had all of this information, nor could they have and fit on a
page. I was looking for a
selection of these that painted a coherent and informative picture of the level
of danger of radioactivity.