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Energy Across Systems
Pre-Learning Concept Check
Below are several statements. Decide which of them you agree with
them or disagree with the statement. Write a sentence or two describing
the reasoning behind your choice.
A. When a wave strikes a substance, its energy will be absorbed.
AGREE
DISAGREE
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B. When a wave is absorbed by a substance, its energy is used up.
AGREE
DISAGREE
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C. All frequencies of EM waves are absorbed by the same substances.
AGREE
DISAGREE
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D. Energy that has been absorbed by a wave can be re-emitted by the
substance.
AGREE
DISAGREE
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Investigation # 7
Pre-Learning Concept Check
CORRECT RESPONSE(S):
A. Students should DISAGREE with this statement. When a wave strikes an
object, it may be reflected off of the substance or the wave may enter the
substance. If it enters, the energy may be absorbed by the substance or
the wave, and its energy, may simply transmit through the substance.
B. Students should DISAGREE with this statement. Energy is never used
up, it must go somewhere. Often, energy is transformed into thermal
energy but it is never “used up.”
C. Students should DISAGREE with this statement. Every substance
responds differently to waves, mechanical and electromagnetic. The
substance’s response to the wave is determined by its molecular
structure. This is called selective absorption and is the topic of
Investigation #7
D. Students should AGREE with this statement. When a wave enters an
object, called refraction, it can be totally absorbed or partially absorbed by
the substance. The absorbed portion generally ends up as thermal
energy. In many cases, a portion of the energy is allowed to transmit
through the substance OR a portion of the absorbed energy is re-emitted
in a different wave. For example, a visible light wave may be absorbed by
a substance and the substance my re-emit a portion of this energy as an
Infrared light wave.
STANDARD(S) ADDRESSED:
Standard #3, Strand #1
3.1.3
Mechanical waves result from the organized vibrations of molecules in substances.
Kinetic energy can be transferred very quickly over large distances by mechanical waves.
Standard #3, Strand #3
3.3.3.
Waves (e.g., sound and seismic waves, waves in water, and electromagnetic waves)
carry energy that can have important consequences when transferred to objects or
substances.
3.3.4.
When waves interact with materials, the energy they transfer often leads to the formation
of other forms of energy. These interactions, which depend upon the nature of the
material and the wavelength of the waves, can be used to create practical devices (e.g.,
sonar and ultra sound imaging, solar cells, remote control units, and communication
devices).
Investigation # 7
Pre-Learning Concept Check
WHAT DOES RESEARCH TELL US?
The topic of selective absorption and selective reflection of waves has a
significant influence on our daily lives. We frequently design devices that absorb
certain types of waves and other devices that reflect other types of waves.
Selective absorption is present in many other contexts as well; one great
example is the process of photosynthesis where light waves in the range of the
color green are reflected while the other colors are absorbed by the plant.
Research on students’ understanding of waves, in specific selective
absorption, is very limited. As in the last investigation several of the sources of
confusion were listed by Dr. Joseph Stepans (1996) in his text Targeting
Students’ Science Misconceptions.
1. Scientific models used to teach the concepts of matter are abstract.
2. There often is unexplored conflict between students’ everyday
experiences and the classroom or textbook presentations.
3. Some of the language used by teachers and textbooks may confuse some
students.
4. Many students, even those at the college level, extend macroscopic
properties like color and hardness to the atomic/molecular level.
5. Instructional materials used to convey abstract concepts are often twodimensional diagrams with symbols.
6. Models made of common objects, such as toothpicks, marshmallows,
Styrofoam balls, or nuts and bolts may lead students to literally transfer
the attributes of the models to what they are supposed to represent.
7. Many students lack the formal level of thinking and spatial skills to make
sense of the textbook representations, instructional models, and
demonstrations about matter and the behavior of matter.
INSTRUCTIONAL IMPLICATIONS:
Many students will think that all waves are absorbed by substances, often
overlooking the reflected piece. Demonstrating the reflected wave and the
refracted wave (which will either be absorbed or transmitted) will provide
students with a mental picture of selective absorption / reflection. Probing
discussion during this time will provide a firm foundation for students as they
struggle for understanding in this early stage. Energy chains and energy
diagrams can also be used to communicate that the energy carried by the wave
doesn’t disappear or “go away.” Providing a number of practical examples of
both selective absorption and selective reflection will also be beneficial.
Investigation # 7
Pre-Learning Concept Check