• required: "Physics", Cutnell & Johnson, Volume 2, Fifth Edition
• optional: "Student Solutions Manual", Cutnell and Johnson

• 29:11 or equivalent
• Algebra and trigonometry at the level of Appendices A-E of the text

Q4

Electron Diffraction

Geiger Counters and Radioactive Shielding

E4

Exam 1 scores:

• Your score is now posted on WebCT. Instructions on how to use WebCT appear above. The systems administrator tells me that WebCT will be down from 10 PM this evening to 4 AM tomorrow morning.
• The maximum possible score was 15, and the highest actual score was 14. The mean score was 8.7, or 58% of the maximum possible. A histogram of grades is here.
• A table listing the percentile in the class is here. Example: if you received a grade of 6 you can use this table to see that you were in the 20th percentile, meaning that 20% of your classmates scored the same or lower than you. Your percentile standing in an exam is not used in computing your course grade; it merely serves as an indicator of how well you are performing as compared to your classmates.

• Exam 1 questions and the answer key now appear in a pdf file on WebCT. They will remain there for the remainder of the semester, so that you may view them when studying for the Final Exam. They are combined into a single view-only pdf file.
• The WebCT systems administrator advises that WebCT is often going down, mainly at night for maintenance to correct a hardware problem; she hopes these outages will be over soon.

Exam 2 scores:

• Your score is now posted on WebCT. Instructions on how to use WebCT appear above.
• The maximum possible score was 15, and the highest actual score was 13. The mean score was 7.9, or 53% of the maximum possible. A histogram of grades for exam2 is here and for the total of exams 1 and 2 is here.
• A table listing the percentile in the class is here.

Exam 3 scores:

• Your score now appears on WebCT.
• The maximum possible score was 15, and the highest actual score was 15. The mean score was 8.9, or 59% of the maximum possible. A histogram of grades for exam 3 is here and for the total of exams 1+2+3 is here.
• A table listing the percentile in the class is here.

re. the number of labs that are graded:

If you haven't done 13 labs already, I recommend that you take the makeup lab. Otherwise you will receive a zero for the lab you missed.

Here is how it works:
There are 13 labs, and your lab grade is based on those 13 labs. No grade is dropped in computing your grade for the lab portion of the course. If you've done 12 or fewer labs, you may take the makeup lab next week to replace the zero for a lab you missed. If you've done 12 labs, you may elect to not do a 13th but you will receive a zero for the one you miss. You must do at least 12 labs to pass the course.

There was some false information out there:
One of the TAs informed me today that he previously told his students that he will compute the lab grade using only the 12 highest lab scores, dropping the lowest score if a student does 13 labs. He was mistaken. His plan would have resulted in his students having a grading advantage as compared to students with the other TA. I have asked this TA to remedy this error by emailing his students today, to recommend that they take the makeup lab next week if they have missed a lab. If a student of this TA has missed two labs, we can arrange an additional makeup lab. With this solution, students of one TA are not favored over those of the other.

In a related matter, a student asked me whether he can take the makeup lab even though he has done all 13 labs in order to drop the lowest of his 13 lab grades. The answer is no. The syllabus does not allow for dropping any grades.

All four pages of formulae for the final exam are now here In the Final Exam, you will be provided these four pages, consisting of the same pages you already had for Exams 1, 2, and 3, plus a new page for Chapters 31 and 32.

Homework assignment for Chapter 32:

• Problems: 2, 4, 34, 35, 36, 37, 50, 52
• Conceptual Questions: none

Solutions for Homework problems in Chapters 31 and 32 will appear on WebCT one day earlier than the day indicated on the lecture schedule.

regarding the number of labs that are graded:

The following information replaces the announcement of 4 Dec. that appears above:

I'm reducing the requirements for the lab portion of the course.

Here's the new grading policy for the labs:

Only your best 12 labs will count. If you take more than 12 labs, I will use the best 12. If you take only 12 labs, I will use all 12. (This represents a change from my original plans, which were to use 13 labs in computing your course grade, without dropping any grades.)

One thing that remains unchanged is that you must do a minimum of 12 labs to pass the course.

This change is the result of my discovering that over half the class believed that only 12 labs would be used in computing the course grade. I discovered this problem originally on Wednesday, when I thought it affected only the students of one TA. Today, after lecture, I discovered that it also affected at least half the students for the other TA as well, judging from the attendence for the 13th lab (Geiger Counter).

To solve the problem, my criteria are to treat students equally so that students of one TA are not favored over students of the other TA, and also to minimize disruptions in your plans. This leads me to make the change described above.

Regarding the make-up lab scheduled for the last week of classes, anyone can take this makeup lab. If you have more than 12 lab grades as a result of taking the makeup lab, I will use the best 12 lab grades.

If you have any questions, please feel free to ask me.

Course grades are now posted on WebCT. Letter grades were assigned as described above.

How your grade was computed:
The column labeled "total weighted" score was computed as 0.75*examtotal% +0.25*lab% where the 0.75 and 0.25 are the weighting factors described above; examtotal% and lab% are ratios of your scores as compared to the maximum possible. I then ranked everyone's total weighted score from top to bottom, and used the College scale described above to assign letter grades. Grades very close to borderline between letter grades were given either a + or a - shading so that the total number of grades with a + shading is the same as the total number of grades with a - shading; most students received a grade that was not shaded.

Histograms appear here:

• final exam (max possible 25, average 14.7 = 58.8%)
• lab scores best of 12 (max possible 1200, average 1174 = 97.8%)
• total weighted score (max possible 100%, average 68.1%)

Note that lab scores had an extremely compressed distribution whereas the exams had a very wide distribution. The two distributions had standard deviations, compared to their mean, of about 1% and 30%, respectively. Consequently, your course grade, which was determined by rank in class, was affected very little by your lab score. Indeed, if one were to swap the best total lab score for the worst,among students who did 12 labs, it would have about the same impact on the course grade as missing just one question on an exam.