Welcome to the Post-lab.
Dr. Harry Shipman is on-hand to begin your de-briefing.
Let's
hear what he has to say.
Summary of Events
During the in-class laboratory activity you
manipulated materials which can support a number of arguments relevant
to the mission you have been assigned in the PBLCenter. The post-lab
summarizes those arguments and contains links to various media helping
you to recall what was accomplished during the in-class lab. Let's
take a look, once again, at the arguments.
Arguments
Argument #1: The length
and direction of a shadow can show you the angle and direction of the light
source which is casting the shadow.
Explore the two links below to show images
of short shadows and long shadows. Notice the position of the flashlight,
which is casting the shadows, in each situation.
Argument #2: When light comes
from a direction close to overhead, it is more concentrated than is the
case when it comes in at a slant, at a large angle from the overhead direction.
Access the flashlight
/ graph paper animation by which you can control the direction of a
light source and see the surface area it illuminates. In the classroom
laboratory you did the same thing with a real flashlight and a piece of
graph paper. You can certainly perform this same activity at home, should
you wish to review it; all you need are a flashlight and a piece of graph
paper.
Many introductory textbooks refer to light
that comes from a direction close to overhead as "direct sunlight" and
light that comes in on a slant as "indirect sunlight." Those terms
have not been used during this e-lab because experience and science education
research shows that some students associate direct and indirect sunlight
with something rather different.
Argument #3: Many people
think that seasons are caused by the changing distance of the earth from
the sun.
Consider
the following web page which provides some data demonstrating how the
earth's distance from the sun changes very little during the year.
In fact, the earth is very slightly closer to the sun in January, during
winter in the northern hemisphere.
Argument #4: The length
and direction of shadows depends on what time of year it is, and where
you are on the earth.
In-class, you performed some experiments with
globes, lights shining on them (to represent the light from the Sun), and
little pins on the globes (which represent objects that can cast shadows),
to show what happens to shadows at various places on the earth during different
times during the year. Access the two links below to view video clips
illustrating what shadows do at different times of the year from Newark,
Delaware.
These arguments can be used to support
your answers to the problem which is presented to you in the PBLCenter.
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