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A c t i v i t y 2 – L i g h t f r o m A f a r
Math Concepts
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Graphical representation of data
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Comparing predictions to data
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Inverse square relationships
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Sources of error and their effects
Materials
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CBL 2™
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TI Graphing Calculator
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6-inch unit-to-unit link cable (or any length)
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TI light sensor
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(Incandescent) 60 Watt light bulb and light socket
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Ruler or tape measure
Introduction
You've probably noticed that the intensity of light from a light bulb decreases as
you move further away. Theoretically, the intensity of light I is related to the
distance d from the light source by a function of the form:
where the value of the constant A depends on the light bulb. In this experiment
you will compare theoretical predictions with actual measurements.
You will need a TI light sensor (included with the CBL 2) to measure light intensity.
You can use either a tape measure or a measuring stick (a yardstick or a meter stick)
to measure distance.
Set-up
You will need a relatively dark room. Place a bare light bulb at one end of the room
with a dark background behind it. You will measure the intensity of the light from
this bulb from various distances.
© 2000, 2003 T
I
EXAS
NSTRUMENTS
Science Concepts
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A
I =
d
I
NCORPORATED
Data collection and analysis
Measurement of light and distance
2
G
S
ETTING
TARTED WITH THE
CBL 2™ S
41
YSTEM
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