Light and Sleep Lesson #2
Objective: Quantitatively define the amount of light and timing of light you are receiving
throughout the school day and how it acts as a circadian stimulus by planning and
conducting an investigation designed to quantify the amount of light you receive during a
school day.
Warm-Up: Define and give examples of circadian rhythms in animals and humans.
Procedures
1. The stimulus shows the average light exposure for 23 eighth grade students. The
light gray area represents the circadian stimulus, which was exposure to light. The
black area represents the students’ activity level. You will be interpreting information
in this graph.
Figure 1. The effect of circadian stimulus on activity over time
What is the effect of light exposure on activity?
Why does activity remain high in the evening even when there is a gradual decrease in
stimulus?
What do you think is happening in the absence of light?
2. Analyze and interpret the data you collected in your sleep diary. Discuss any
patterns that emerged. Discuss your sleeping habits. Estimate the amount of sleep
you get per day/night during the week versus each day on a typical weekend.
3. On average, teenagers need 9.25 hours of sleep nightly. How do the number of
hours you are actually sleeping compares to the amount you should be sleeping.
How does it affect you?
4. Calculate when you should be going to bed at night by accessing a Sleep Plan
Calculator from http://www.binfy.com/sleep-planner-calculator.php .
Based on the information you receive from the calculator, are you going to bed on
time?
5. Brainstorm: What do you know about light?
6. Look at the diagram below (Figure 2). This is how scientists diagram light. What
does this diagram tell you about light?
Figure 2. The electromagnetic spectrum.
7. Of these waves/types of electromagnetic radiation, which have more energy?
Support your answer.
8. Recall from the Washington Post article that the circadian system is tuned to shorter
wavelengths; therefore shorter wavelengths reduce the production of melatonin at
night. Since blue light and shorter wavelengths prevent sleep are they detrimental in
all situations? Is there any time that blue light/short wavelengths are beneficial?
Note: Color is not a property of light, but rather the way that sensory receptors
interpret visible light wavelengths. When referring to colors of light, you are
referring to wavelengths of light interpreted as color.
We can use light meters to measure the amount of light in a room or outside. One
way to measure amount of light is in lux. Lux is the SI unit of illuminance, or the
degree to which something is illuminated (this does not refer to the amount of light
radiating from a light source). It is equal to one lumen per square meter when the
data collector is one meter away from the light source.
Test several different light bulbs with different lux readings using a light meter app
(Eden App) for practice. Use the desk lamps with light bulbs that have different
lumen values. Make sure that other light sources are turned off or dampened to
allow for higher accuracy in the readings. Note: Accuracy is determined by the
instrument itself, so no reading will be 100% accurate in this environment with these
tools.
A. Functional Lighting
9. Brainstorm in your small groups to list as many different sources of light as you can.
10. What type of lighting do you think would be best for a planetarium or a movie
theater?
11. What type of lighting do you think would be best if you were designing a bedroom?
12. What type of lighting do you think would be best if you were designing a school?
13. How is light related to a building’s function?
B. Light Sources
14. Look at a variety of bulbs and predict what will happen when you take a reading with
the light meter app. Then take the reading and compare it to your prediction.
Type of Bulb
Wattage
Prediction
Standard 1
Standard 2
LED
Compact
Fluorescent
Plant Light
Black Light
What is the advantage of an energy-saving bulb?
Lux Reading
C. Light Intensity
15. Take 10 readings of a standard light bulb at intervals of every 100 cm; create a data
table and graph your results. What happens to the amount of light received as you
move away from the light source?
16. What factors of light relate to the quality of sleep you get?
17. Plan an investigation to collect baseline data regarding the amount of light that you
are exposed to as they go throughout you school day.
18. Develop a plan for collecting measurable data.