Relativity Links
Neat pictures and graphs
Einstein himself on the subject, a popular account.
Thursday, March 29, 2007
Special relativity applet for today
An applet to explore time dilation and length contraction.
And some follow-up questions.
The questions are due at the end of class.
Tuesday, March 27, 2007
Monday, March 26, 2007
Tomorrow's Lab (27 Mar 07)
Tomorrow we will do a short lab on lenses.
You can find the procedure here.
Also: there is new homework on Webassign, covering Ch. 22 and the first part of Ch. 23 (mirrors). Since I put it up about two days late, you get about two more days - it is due this coming Sunday at midnight.
Exam II scores and distribution.
The second exam is graded, and it went better than expected. The average was 84.64% with a standard deviation of 12.41%, so there was no need for scaling. The usual 90/80/70/60 scale applies.
In the end, each of the 8 questions you answered was worth 10 points, for a total of 80 points. Full credit on the bonus question was 5 points extra. Heavy partial credit was given, including on the bonus question. Below is the grade scale out of 80, for convenience:
> 72/80 = A
> 64/80 = B
> 56/80 = C
> 48/80 = D
< 48/80 = F
Pluses and minuses are given at +/- 2.5% from the grade breaks (e.g., 97.5% = A+, 87.5% = B+, 92.5=A-).
Below is the histogram for the exam. Quite a few A's and C's. There were only 3 failing grades, and the lowest of those was only 5 points from passing - 5 points which can easily be made up if you rock the homework (hint, hint).
Next is a plot showing the percentage of students choosing each problem, and the average score for that problem. Clearly, numbers 1, 8, and 9 were tough. Numbers 10 and 12 were sleepers - the few who answered them did very well, disproportionately so, but they were largely ignored. Otherwise, there were no surprises as to which problems you chose, and the scores were in proportion.
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