Activity
Day
1
1. Write this question on an overhead or on the board:
“Can microwaving your food give you cancer?”
2. Let students react to question and discuss as a class what they know about
the topic. Is it true? If microwaving doesn’t cause cancer, is it bad for
you in other ways?
3. After students have expressed opinions and thoughts, remind them that “basic
concepts and principles of science and technology should precede active debate
about the economics, policies, politics, and ethics of various science- and technology-related
challenges. “ (NSES 1994) What do they know about the science behind microwave
ovens?
4. Review ideas on previous lesson titled “The Wonderful World of Waves.” This
is an opportunity to address some concepts students didn’t explore in the
previous lesson. Ask students what happened to the far end of a medium (i.e.,
the jump rope, telephone cord, etc.) as a generated wave reached it. They should
say it moved, and if there was movement, then there was a force, so there was
energy. The idea is a wave transmits energy.
5.
If any groups studied speed of waves in the previous
lessons, they may have noticed some mediums transmitted
waves more quickly than others. The “lighter” the
medium was, the wave should have traveled faster. For example, a wave will travel
faster through a piece of string than through a heavy jump rope.
Electromagnetic
waves can travel through a vacuum, which is at the extreme far end of a “lightness” spectrum,
having no mass. Therefore, they go very fast--at the speed of light. This is
not an exact scientific explanation, but it will make the point.
6. Ask students the following question:
A wave has a wavelength of three feet and a frequency of two hertz. How fast
is the wave traveling?
Hints—Think about the algebraic formula for speed and try drawing a diagram
of the two wavelengths.
Give students sometime for this question and monitor the class to steer them
if necessary. If they draw an appropriate diagram, they should see the connection.
If two full wave cycles are propagated each second (that’s what two Hertz
describes) and each one is three feet long, then the wave must be traveling
at 6 ft/s.
Speed =  where is the  frequency,
and  is the wavelength
7. Students make the connection to electromagnetic waves. All electromagnetic
waves travel at the speed of light. Thus, the following must be true:
c =
where c is the speed of light, is
the frequency, and is
the wavelength
8. Have students go to the website listed above titled spectrum applet. This
applet allows them to see there is a relationship between frequency and energy.
If they are related, there must be some mathematical formula including them.
Introduce Plank’s constant and the following equation:
E=h where
E is energy, h is Plank’s constant, and is
the frequency
9. As a class practice problems using these two formulas. There are some on the
website titled practice problems, about two or three pages down (it is a large
Adobe (PDF) file). The rest of the day could be used for working on these problems
for homework.
Day 2
1. Review formulas students were introduced to in yesterday’s class by
going over homework problems. Answer questions students might have.
2. Have students return to website titled spectrum applet. Use this as a resource
and begin a table in their notes including each major type of radiation, what
its sources are, how it’s measured, and leave a column for possible environmental
health risks. List the wave types from low to high energy.
3. Once students have completed the table (except for the environmental health
column), have them look at the website titled microwave applet. This is a good
demonstration of how a microwave passing through a water molecule causing the
molecule to vibrate. Remind them of the polarity of a water molecule.
4. Assign two or three students (depending on the class size) to each type of
electromagnetic wave. Ask them to research the potential environmental health
risks associated with them and to be prepared to present their findings to the
class. They should find at least two sources in order to confirm any information
discovered.
5. Have each group present what they found and ask them to fill in the rest of
their note chart as information is presented.
Closure
Ask class what patterns they notice with environmental
health risks. If they conducted good research, they should
notice the higher the energy level of radiation, the
greater potential risk. Ask them to note where microwaves
are on the spectrum. What common waves are closest? Ask
students again whether they think microwaves can have
environmental health risks. What exposure to microwaves
do microwave ovens and micro-waved food provide to users,
if any?
Homework
Practice
problems using and E=h and
c = for
homework on the first night.
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Embedded
Assessment
Students
ability to achieve standards can be assessed based on class
discussions and first night’s homework.
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