Name
Class
Date
Solar Angle and Light Intensity Minilab
For this activity, you will use either a flashlight or a cellphone with a flashlight feature
along with an index card with a small hole.
Directions:
Go through each step carefully and thoughtfully.
Step 1: Observe and Ask Questions
1. Hold the index card so that the hole aligns with the light coming from the
flashlight or your cellphone. This will contain the light in a smaller area.
Position A
Flashlig
ht
Position A
90*
90*
2. Keeping the card and light source together, change the angle that the light is
coming from. Do this several
times.
Position B
Position
B
45*
45
*
3.
Record your
observations: What happens to the size and shape of the light on your desk?
Step 2: Experiment and Gather Data
1. Hold your light source and index card in Position A about 10 cm from the desktop.
Position A is a 90 angle.
2. Use your ruler to measure the length and width of the brightest part of the light
beam. Measure to the nearest 0.1 cm. Repeat twice more. Record your measures
below:
Measurement
Trial 1
Trial 2
Trial 3
Length (cm)
Width (cm)
3. Change the angle of your light source and index card in Position B. Position B is a
45° angle. Use a protractor to check. Try to keep the distance from the light
source to the desk about 10 cm. (This may be tough, but do your best!)
4. Use your ruler to measure the length and width of the brightest part of the light
beam. Measure to the nearest 0.1 cm. Repeat twice more. Record your measures
below:
Measurement
Trial 1
Trial 2
Trial 3
Length (cm)
Width (cm)
Step 3: Analyze and Interpret Data
1. Calculate the mean (average) length and width of the brightest part of the light
beam when the light source is at a 90° angle and at a 45° angle. Record the means
(rounded to the nearest 0.01 cm) below:
Measurement
90°
Mean Length (cm)
Mean Width (cm)
2. Which angle produced the most intense (concentrated) light?
45°
Step 4: Construct Explanations
1. Why was it important to try to keep the distance of the light source from the
desktop the same?
2. Based on your data, what can you conclude? How does the angle of the light source
affect light intensity?
As the angle increases, the intensity of the light
_______________________.
Step 5: Communicate
1. Discuss your conclusions with your neighbors. Did they come to the same
conclusion?
Step 5: Engage in Argumentation from Evidence
Prompt: How does light angle affect light intensity?
Claim
Write an answer to the
question or prompt. Make
sure that you include the
prompt in the sentence.
Evidence 1
Use evidence from your
experiment or from a
classmate’s experiment to
support your claim.
Reasoning 1
Use scientific principles to
explain why the evidence
supports the claim.
Step 6: Make and Use Models
1. On the back, draw and label a model to explain what happens to light intensity when
the angle of light changes.
How Light Angle Affects Light Intensity
What does all this have to do with the seasons? Find
out tomorrow!