Page 421 - Canadian BC Science 9

How Wide Is the Sun? Conduct an INVESTIGATION Inquiry Focus
11-3C
SkillCheck
• Observing
• Measuring
• Evaluating information
• Working co-operatively
Safety
• NEVER look directly at the Sun under any
circumstances.
Materials
For each group:
• metre stick
• 2 squares of cardboard
(20 cm 􏰀 20 cm), one with a
1 cm diameter hole
• white paper (6 cm 􏰀 6 cm)
• aluminum foil (4 cm 􏰀 4 cm)
• clear adhesive tape
• pin, or mechanical pencil
• ruler
• pencil
• calculator
The Sun is about 150 million km away from Earth. In this activity, using a simple tool and some straightforward arithmetic, we can produce a very accurate calculation of the diameter of the Sun.
Question
How can you determine the diameter of the Sun?
Procedure
1. Use the metre stick, cardboard, paper, aluminum foil, and tape to assemble the apparatus shown here.
Step 1
3. Move outdoors. Steadying the apparatus against your stomach, aim the aluminum foil end toward the Sun. Try to capture the image of the Sun’s disk in focus on the white paper.
4. Have your partner use a pencil to mark the diameter of the Sun’s image on the white paper.
5. Repeat step 4 two or three more times.
6. Measure the diameters you have marked off and calculate an average diameter.
Analyze
image dD
100 cm 150 000 000 km
1. To calculate the Sun’s diameter, use the average diameter you have measured in the following formula.
d 􏰃 D d = diameter (cm)
100 cm 150 000 000 km D = Sun’s diameter (km)
2. Your teacher will provide you with the accepted value. Use that to calculate your percent error.
% error = actual diameter – calculated diameter 􏰀 100% actual value
Conclude and Apply
1. (a) What was your calculated percent error?
(b) Doyouthinkyourpercenterrorisreasonable?Explain.
2. What do you think were sources of error in this activity?
3. Suggest ways the activity could be improved to lower your percent error.
metre stick
white paper to sketch on
tape
hole in cardboard covered with foil
2. Using the pin, carefully poke a small hole in the aluminum foil.
pinhole Sun
to Sun
Chapter 11 The components of the universe are separated by unimaginably vast distances. • MHR 403