welcome… …to environmental physics i.. important note the next few slides summarize important...
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Welcome…
…to Environmental Physics I.
Important Note
The next few slides summarize important information contained in the course syllabus. Please refer to the syllabus for details.
If there is any discrepancy between these slides and the syllabus, the syllabus is the “official word.”
The on-line syllabus is the “official” official word.
PHYSICS 6Environmental Physics I
Spring 2012
Dr. Allan PringleCourse Instructor
Room 122 Physics, 341‑4031
[email protected]://campus.mst.edu/physics/courses/6/
Course Description
Phyics 6 is a course for non-science majors which will consider, without mathematics, the production of energy and the environmental consequences of its use, and the physical problems associated with pollution.“Without mathematics” means you will not see long derivations, use calculus, or have 5 mathematical homework problems assigned daily.
“Without mathematics” means you will not see long derivations, use calculus, or have 5 mathematical homework problems assigned daily. It does not mean you won’t see any numbers in this class!
Text
The text we will use is Environmental Issues, third edition, by McConnell and Abel, Prentice-Hall, publisher.
There is no text for most of the material I will lecture on. All of my lecture notes will be available on the web, and I will direct you towards (or expect you to find on your own) additional reading and research material.
Course Schedule
Physics 6 meets from 4:00-5:15 pm, Monday and Wednesday in room 227* Fulton Hall. A tentative calendar for the course is included with the syllabus.
Graded Assignments
There will be two major graded assignments due from students. Before spring break you will complete and hand in one “Issue” from your Environmental Issues text.The last two class meetings are set aside for student oral reports on environmental science topics of your choice.
*Except when we meet in 104 Physics.
The “Issues” report and the oral report will each count 25% of your course grade.
Beginning January 25, each day you attend will count 1.0% of your semester grade, up to a total of 22%. There are 26 class meetings January 25 and after. That means you can have four absences during the semester without affecting your grade. Because of this, there will be no excused absences for this course.
Brief homework assignments, quizzes (maybe), and reports on videos we watch will account for the remaining 28% of your course grade.
You may work in groups on these projects; in fact, I will encourage group work.
Course Grades
Letter grades for Physics 6 will be assigned as follows:89.5% - up A79.5% - 89.49% B69.5% - 79.49% C59.5% - 69.49% DBelow 59.5% F
There is no limit to the number of A's, B's, etc.
Attendance 22%Homework, video reports 28%Issues report 25%Oral report 25%
Total 100%
Assignment Due Dates
The last day to drop this class without a withdrawal showing on your transcript is Monday, February 20, 2012. The last day to drop this class is Friday, April 6, 2010.
Any student who has inadequate attendance, as evidenced by missing a total of 5 graded assignments of any kind, will be placed on Academic Alert. Students who fail to take the recommended action are subject to being dropped if a subsequent assignment is missed.
Dropping Physics 6
Some dates are given in the syllabus. We will discuss these as the semester proceeds.
Unresolved Complaints
You can send e-mail to me at [email protected]. You are welcome to turn in homework electronically.
It is hoped that any complaints about the course can be resolved in a collegial manner through discussions between student and instructor. However, if there are any complaints that cannot be resolved, you may take them up with the Physics Department Chairman, Dr. Dan Waddill ([email protected]).
Jan. 9The Scientific
Method
Jan. 11Measurements
Jan. 16no class
Jan. 18Matter and Mass
Jan. 23Climate Changes Video (104 Phys.)
Jan. 25Video DiscussionMatter and Mass
Jan. 30Force and Motion
Feb. 1Force and Motion
First Four Weeks Schedule
No Physics 8 Lab this week!
Some final observations, before we start the course material…
Nature follows the laws of physics, regardless of how you feel it should act.
There is one* right answer to any physics problem. All other answers are wrong.
Learn from your mistakes and your successes.
There’s nothing wrong with starting off ignorant about something important. Just don’t stay ignorant!
*Except for estimation and order of magnitude problems. Unfortunately, it may not be possible for humans to discover the one right answer.
Physical Science:The Scientific Method
What is science? Write your definition on one side of a piece of paper and turn it in when we take a break. You don’t need to put your name on the paper.
There are lots of ways to define science, but I like this one:“Science is the process of seeking and applying knowledge about our universe.”
“Science is the process of seeking and applying knowledge about our universe.”
Science is a process.
Physicists have traditionally been more interested in the “seeking” part and not as interested in the “applying” part…
…except when it comes to getting research funding.
Unfortunately, this definition offers no clues about the intuition and creativity needed to do science.
“Science is the process of seeking and applying knowledge about our universe.”
Science is not the body of knowledge that humans have accumulated about the universe.Science is not a collection of facts and equations in a book.
Science is not a collection of trivia and numerical recipes to memorize.Science is not a collection of trivia and numerical recipes to memorize. Ugh!
People like to say “science says blah blah blah…” because it’s written in a book somewhere.
Nonsense! Science doesn’t talk. People talk!
A science or engineering book about an active area of research is likely to be outdated…A science or engineering book about an active area of research is likely to be outdated… or maybe even wrong.
Does that mean there’s no “truth?”
We do science under the assumption that the universe follows basic universal laws, and that we can discover them.
What is the scientific method? Write your definition on the other side of your “definition of science” paper and turn it in when we take a break. You don’t need to put your name on the paper.
As long as we’re putting things on paper, how about doing this:
How much do you agree (5 = strongly agree) or disagree (0 = strongly disagree) with the statement below?
Your Physics 6 instructor is a “tree hugger.”
What is the scientific method? Write your definition on a piece of paper and turn it in when we take a break. You don’t need to put your name on the paper.
observations,
gathering information
questions,hypothese
s
theory!mathematic
s!
newstuff
EXPERIMENT
observations,
gathering information
questions,hypothese
s
theory!mathematic
s!
newstuff
The foundation of science is experiment.Physics is an experimental science.
EXPERIMENTEXPERIMENT
observations,
gathering information
questions,hypothese
s
theory!mathemati
cs!
newstuff
EXPERIMENT
Without theories, experimentsare like collections of trivia.
theory!mathematic
s!
observations,
gathering information
questions,hypothese
s
theory!mathematic
s!
newstuff
EXPERIMENT
Theory must not only explain everything that is known…
…it must also predict that which is not yet known.
newstuff
theory!mathematic
s!
newstuff
EXPERIMENT
When does a theory become accepted by scientists? When it can successfully explain observed phenomena and when it can successfully predict new phenomena.
If your new theory can't do both, don't take offense if nobody accepts it.
Theory or Law?
Eventually, after a theory has been verified over and over by enough experiments, we may start to believe it represents some fundamental truth about the universe.
theory!mathematic
s!
EXPERIMENT
newstuff We express this
truth as a Theory or Law.We believe a theory because it “works.” Theory
or Law
A Law is more likely to be expressed in a brief statement (words or equations), such as Newton's second law.
F ma
A Theory is more likely to need many pages of mathematics for its expression.
We may think of laws as being the foundations of theories, but both ultimately depend on our (typically imperfect) observations and measurements of natural occurrences.
I have a question for you!
Who decided what the scientific method is?
Homework Assignment #1 (due Wednesday, January 11). What is Occam's Razor? I do not want an essay. A few clear, concise sentences will be sufficient. You can do this assignment with an Internet search, but I stongly recommend you not stop your search after the first site you find, because there are many different views of Occam's Razor. You may print out your search results, and add a sentence or two of your own comments.
Law or empirical relationship?
The job of a theorist is to take accepted laws and theories and use them in combination with new ideas to explain and predict new phenomena.
It is critical to distinguish between empirical relationships and true laws.
I will take an example—the photoelectric effect, usually taught in Modern Physics classes—to illustrate this.
Light striking a metal anode in a vacuum tube causes electrons to be emitted from the anode.Because the electrons are “kicked off” with considerable kinetic energy, some of them reach a nearby cathode, in spite of its negative voltage.
anode: a fancy name for a positively charged metal plate
cathode: a fancy name for a negatively charged metal plate
A
x
+ -
V
- - --
- -
You can use an ammeter to measure the current reaching the cathode.
A
x
+ -
V
You can make the cathode voltage more negative and see how that affects the current.
- - --
- -
You can make the cathode voltage negative enough so that no "photoelectrons" reach the cathode.
So what? Light gives energy to electrons in the anode. Because the electrons have energy, they escape the anode, even though it is positively charged and attracts electrons. If the electrons get enough energy, they can even reach the cathode, in spite of the fact that it is negatively charged and repels electrons.
A
x
+ -
V
- - -
The figure below shows a plot of the maximum photoelectron energy versus frequency of incident light.
This is great! Physicists like puzzles!
Tell me what you see or think when you look at this plot.
The figure below shows a plot of the maximum photoelectron energy versus frequency of incident light. The higher the frequency of light waves, the greater the energy contained in them. Classical physics predicts a parabolic, not linear line shape (starting at the origin).
The figure below shows a plot of the maximum photoelectron energy versus frequency of incident light. The higher the frequency of light waves, the greater the energy contained in them.
incoming light energy
ejected electron maximum energy
You can do the experiments for a wide variety of metal anodes, and find the lines have the same slope for all metals.
The lines all obey the relationship . 0max hfhfK
Tell me what you see or think when you look at this plot.
This is an empirical equation—it fits the experiment, but we haven't explained anything.
, 0max hfhfK where h is the slope, f is the frequency of the incident light, and f0 (v0 in the figure) is the frequency below which no photoelectrons are emitted; h has the same value for all metals, but f0 depends on the metal.
In this context “empirical” means “depending on observation alone, without regard to theory” but not “derived from observation or experiment.”
The last sentence on the previous slide is important, so let me repeat it:
0max hfhfK
This is an empirical equation—it fits the experiment, but we haven't explained anything. This is an empirical equation—it fits the experiment, but we haven't explained anything. It might even be wrong!
While studying the photoelectric effect during the late 1800’s, physicists found a phenomenon which could not be explained by the physics of the day; in particular, the straight line shape of the electron energy plots, which don’t start at the origin.
We found an empirical equation which explains the straight line shapes. We found an empirical equation which explains the straight line shapes. No we didn’t. The equation models our data. It doesn’t explain anything. It might even be wrong.
In the early 1900's Einstein was able to explain the photoelectric effect by assuming that light comes in little packets or "particles" of pure energy.
The energy of one of these light "particles" is E=hf.
An electron can absorb all of a photon's energy or none of it, but nothing in between. The maximum energy electrons can leave the metal with is equal to hf minus the amount of energy needed to escape from the metal.
Thus, according to Einstein
max 0hf K hf
incident photon energy
energy “spent” to escape
energy left
You are in jail. It costs $50 to get out of jail. I give you $80. You get out of jail and have $30 left.
I don't care if you remember the details of the photoelectric effect or the equations.
I do want you to understand the difference between an empirical equation and a theory.
Einstein's theory of the photoelectric effect brilliantly explains all of the features of the photoelectric effect, but the idea was so revolutionary in 1905 (when he introduced it) that it wasn't really accepted for more than a decade.
Even physicists using Einstein’s "quantum theory of light" to solve other problems figured that eventually the true explanation would be discovered and the quantum theory could be thrown out.
This presentation leaves out some details! Search the web if you are curious.
It took a large body of experiments and predictions of new phenomena to convince them otherwise.
During this class, you will encounter a lot of people who want to draw sweeping conclusions from their data.You should always ask questions like:
How did they get their data?
How reliable and reproducible is their data?
Can anyone else reproduce their data?
Are there alternative explanations for the data?
Using the data presented, can you make predictions and do new measurements to confirm the conclusions?
Don't be fooled by people who claim their new theory is rejected because it is so revolutionary.
New theories are rejected because they are not supported by experiment, because they are unnecessary, or because they are tired old incorrect theories in a new disguise.
Homework Assignment #1 (due Wednesday, January 11). What is Occam's Razor? I do not want an essay. A few clear, concise sentences will be sufficient. You can do this assignment with an Internet search, but I stongly recommend you not stop your search after the first site you find, because there are many different views of Occam's Razor. You may print out your search results, and add a sentence or two of your own comments.
Reminder…