
Only the Shadow Knows
Ainsley Adams 


68 
Three 45minute class periods 

Have you ever been followed by your shadow? Or have you ever followed
it? Shadows are formed because light travels in straight lines. On cloudy
days, it can seem as if there are no shadows at all. Yet on a clear day,
if you stand with your back to the sun, you are sure to see your shadow.
Shadows are formed when an opaque object or material is placed in the
path of rays of light. The opaque material does not let the light pass
through it. The light rays that go past the edges of the material make
an outline for the shadow. The center part of the shadow, which gets no
light at all, is the darkest part and is called the umbra. The rest of
the shadow is lighter because it gets light from some parts of the source
of light, and is called the penumbra.
Through the activities presented in the lesson, students will become familiar
with the causes for formation of shadows, an understanding that the shape
and length of shadows are dependent upon the position and manipulation
of the light source. After a close examination of Web sites and video
segments, students, through "free play," will create shadows,
compare the size and shape of the shadow with the actual object, engage
in shadow play theatre, and discover what happens to shadows when there
is much light as compared to little light. Students will measure shadows
and draw inferences from the data collected, and finally, using trigonometric
functions, calculate heights of objects based on the length of the shadow
the objects cast.
Prerequisites:
Students should be able to:
 Use a protractor to measure angles
 Know that a right angle has a measure of 90 degrees
 Identify the sides of a triangle
 Read a table of trigonometric functions
 Divide by decimals
Students will be able to:
 Determine what a shadow is and how shadows are formed
 Measure the size and shape of shadows in relationship to the distance
a light source is from an object
 Determine mathematically the height of an object based on the length
of the shadow the object casts
National
Standard Education Content Standard 58: Science as Inquiry
http://www.nap.edu/readingroom/books/nses/html/6d.html
Design and Conduct a Scientific Investigation
Students should develop general abilities, such as systematic observation,
making accurate measurement, and identifying and controlling variables
.
Develop Descriptions, Explanations, Predictions, and Models Using Evidence
Students base their explanations on what they observe. This allows students
to effectively conduct investigations since developing explanations establishes
connections between the content of science and the context within which
students develop new knowledge.
Use Appropriate Tools and Techniques to Gather, Analyze, and Interpret
Data
The use of tools and techniques including mathematics will be guided by
the question asked and the investigations students design. Students use
computers for the collection, summary, and display of evidence. Students
access, gather, store, retrieve, and organize data using hardware and
software designed for these purposes.
Standard 3 – Mathematics
Students will understand mathematics and become mathematically confident
by communicating and reasoning mathematically, by applying mathematics
in realworld settings, and by solving problems through the integrated
study of geometry, algebra, data analysis, and trigonometry.
Standard 4 – Science
Students will understand and apply scientific concepts, principles, and
theories pertaining to the physical setting and living environment and
recognize ideas in science.
Video:
Reading Rainbow #109: My Shadow
Web sites:
Shape
and Space in Geometry
http://www.learner.org/teacherslab/math/geometry/space/shadows/index.html
Can you judge an object by its shadow? At this site, students are asked
to determine if a shadow can be produced by a particular shape.
The
Shadow
http://www.learningmedia.co.nz/onlineclassres.htm
This Web site allows students to understand how the shadow of a beach
umbrella changes in relation to the sun's position.
Per class:
 Opaque projector
 1 pack copy paper
 Basketball
 Overhead transparency of the poem "My Shadow"
Per student:
 Pencil
 Ruler
 Data Shadow Sheet
 Scissors or hole puncher
Per pair of students:
 Cardboard
 Wood
 Metal cans
 Stones
 Potted plants (small)
 4 large index cards
 Flashlights
The following items should be organized in Ziploc bags and placed in a
basket:
 Flathead screw
 Small funnel
 Perfumesized bottle
 Plastic comb
 Geometric shape toys (ball, animals, trees, cups)
For teacher:
 Obtain copy of Shadows and Reflection by Tana Hoban from local library
or bookstore.

