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 6
Environmental Physics I
Spring 2012
Dr. Allan Pringle
Course Instructor
Room 122 Physics, 341-4031
pringle@mst.edu
http://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. 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.
*Except when we meet in 104 Physics.
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.
The “Issues” report and the oral report will each count 25% of
your course grade.
You may work in groups on these projects; in fact, I will
encourage group work.
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.
Course Grades
Attendance
22%
Homework, video reports 28%
Issues report
25%
Oral report
25%
Total
100%
Letter grades for Physics 6 will be assigned as follows:
89.5% - up
A
79.5% - 89.49%
B
69.5% - 79.49%
C
59.5% - 69.49%
D
Below 59.5%
F
There is no limit to the number of A's, B's, etc.
Assignment Due Dates
Some dates are given in the syllabus. We will discuss these as
the semester proceeds.
Dropping Physics 6
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.
Physics 6 Web Page
Let’s visit the Physics 6 web page.
E-Mail
You can send e-mail to me at pringle@mst.edu. You are
welcome to turn in homework electronically.
Unresolved Complaints
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
(waddill@mst.edu).
First Four Weeks Schedule
Jan. 9
The Scientific
Method
Jan. 11
Measurements
Jan. 16
no class
Jan. 18
Matter and Mass
Jan. 23
Climate Changes
Video (104 Phys.)
Jan. 25
Video Discussion
Matter and Mass
Jan. 30
Force and Motion
Feb. 1
Force and Motion
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. 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… 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
new
stuff
theory!
mathematics!
EXPERIMENT
questions,
hypotheses
The foundation of science is experiment.
Physics is an experimental science.
observations,
gathering
information
new
stuff
theory!
mathematics!
EXPERIMENT
questions,
hypotheses
Without theories, experiments
are like collections of trivia.
observations,
gathering
information
new
stuff
questions,
hypotheses
theory!
theory!
mathematics
mathematics!
!
EXPERIMENT
Theory must not only explain everything that is known…
…it must also predict that which is not yet known.
observations,
gathering
information
new
stuff
theory!
mathematics!
EXPERIMENT
questions,
hypotheses
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.
new
stuff
theory!
mathematics!
EXPERIMENT
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.
new
stuff
theory!
Theory
mathematics!
or Law
We express this truth
as a Theory or Law.
We believe a theory
because it “works.”
EXPERIMENT
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.
+
-
-
-
-
-
-
x
V
A
anode: a fancy name for a positively charged metal plate
cathode: a fancy name for a negatively charged metal plate
+
-
-
-
-
-
-
x
V
A
You can use an ammeter to measure the current reaching the
cathode.
You can make the cathode voltage more negative and see
how that affects the current.
+
-
-
-
x
V
A
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.
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).
ejected electron maximum energy
Tell me what you see or think
when you look at this plot.
incoming light energy
This is great! Physicists like puzzles!
You can do the experiments for a wide variety of metal
anodes, and find the lines have the same slope for all metals.
Tell me what you see or think
when you look at this plot.
The lines all obey the relationship K max  hf  hf0 .
K max  hf  hf0 ,
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.
This is an empirical equation—it fits the experiment, but we
haven't explained anything.
In this context “empirical” means “depending on observation alone, without regard
to theory” but not “derived from observation or experiment.”
K max  hf  hf0
The last sentence on the previous slide is important, so let me
repeat it:
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. 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
hf  K max  hf0
incident photon
energy
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.
energy “spent”
to escape
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.
It took a large body of experiments and predictions of new
phenomena to convince them otherwise.
This presentation leaves out some details! Search the web if you are curious.
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.
Reminder…
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.