Light and Sleep Lesson #2
Table of Contents
Light and Sleep Lesson #2 ..............................................................................................2
Lesson Goal.............................................................................................................................................................. 2
Objectives ................................................................................................................................................................ 2
Standards Alignment ............................................................................................................................................... 2
Time Required ......................................................................................................................................................... 3
Materials Needed .................................................................................................................................................... 3
Prerequisite Knowledge .......................................................................................................................................... 4
Before the Lesson .................................................................................................................................................... 4
Safety ....................................................................................................................................................................... 4
Procedures/Instructional Strategy .......................................................................................................................... 4
Link to Bright Schools Competition (Extend)......................................................................................................... 11
Differentiated Instruction...................................................................................................................................... 11
Appendix ..................................................................................................................... 12
1
Light and Sleep Lesson #2
Grade Level:
Subject:
Writer
6-8
Life Science
McGinnis, Patty
Lesson Goal
Students will quantitatively define the amount of light and timing of light they are receiving throughout the
school day and how it acts as a circadian stimulus.
Objectives
Students will:
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Plan and conduct an investigation designed to quantify the amount of light they receive during a school
day
Analyze their data and make a claim regarding the quality/quantity of light that they are receiving during
the school day
Defend their claim, data, and reasoning to their peers
Describe light and its relationship to sleep
Standards Alignment
Note: This lesson does not fully meet a specific performance expectation of the Next Generation Science
Standards (NGSS) but supports student achievement of the performance expectation listed below. This lesson is
not a full unit of study.
Performance Expectations:
MS-LS1-8. Gather and synthesize information that sensory receptors respond to stimuli by sending
messages to the brain for immediate behavior or storage of memories. [Assessment Boundary:
Assessment does not include mechanisms for the transmission of this information.]
Disciplinary Core Ideas:
LS1.D: Information Processing
Each sense receptor responds to different inputs (electromagnetic, mechanical, chemical), transmitting
them as signals that travel along nerve cells to the brain. The signals are then processed in the brain,
resulting in immediate behaviors or memories.
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Crosscutting Concepts:
Cause and Effect: Cause and effect relationships may be used to predict phenomena in natural systems.
Patterns: Patterns can be used to identify cause and effect relationships.
Graphs, charts, and images can be used to identify patterns in data.
Science and Engineering Practices:
Obtaining, Evaluating, and Communicating Information: Gather, read, and synthesize information from
multiple appropriate sources and assess the credibility, accuracy, and possible bias of each publication
and methods used, and describe how they are supported or not supported by evidence.
Planning and Carrying Out Investigations: Conduct an investigation to produce data to serve as the basis
for evidence that meet the goals of an investigation.
Analyzing and Interpreting Data: Analyze and interpret data to provide evidence for phenomena.
Constructing Explanations: Construct an explanation that includes qualitative or quantitative
relationships between variables that predicts and/or describes phenomena.
Time Required
Two to three 40-minute class periods
Materials Needed
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Background reading about circadian rhythms
 Fact Sheet http://www.nigms.nih.gov/education/pages/factsheet_circadianrhythms.aspx
 Cyclic Behavior of Animals http://www.ck12.org/biology/Cyclic-Behavior-of-Animals/lesson/CyclicBehavior-of-Animals/
Several desk lamps that have light bulbs with different lumen
Free light apps downloaded to iPads, iPhones, or Android devices
Meter stick
Graph paper
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Prerequisite Knowledge
Students are able to define and give examples of circadian rhythms in animals and humans.
Students need an understanding of the electromagnetic spectrum.
Before the Lesson
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Be sure to have introduced circadian rhythms through Bright Schools Lesson #1 before teaching this
lesson.
Collect and set up materials needed.
Print out the two different wavelength lines in the Explain section below.
Test the light meter app to be able to explain to the students how to use it.
Safety
When collecting sleep data, discuss with students the importance of accurately logging their normal sleep data.
The sole purpose of the sleep log is to collect baseline data. Students are not to vary their sleep pattern from
their normal sleeping habits.
When measuring light, students should never look directly at the Sun. Lamps and light bulbs can get hot; students
should not touch them, as they are a burn hazard.
Procedures/Instructional Strategy
ENGAGE
Note: Prior to this lesson, the concept of circadian rhythm should have been introduced. Circadian
rhythms are regular changes that occur over a 24-hour time period. Many species, including humans, are
regulated by an internal clock that dictates sleeping and waking patterns, blood pressure, body
temperature, and other vital functions. This internal clock also controls the production of melatonin, a
hormone that makes us sleepy. A lack of light stimulates the body to make more melatonin, while the
presence of light signals the body to decrease melatonin production. Some species show seasonal
rhythms in additional to daily rhythms. Seasonal rhythms include behaviors such as migration and
hibernation.
1. Show students the graph below. Explain that 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. Tell students they will be interpreting information in
this graph.
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Figure 1. The effect of circadian stimulus on activity over time. (MG Figueiro, JA Brons, B Plitnick, B Donlan, RP Leslie and MS Rea.
Measuring circadian light and its impact on adolescents, Lighting Res.Technol. 43(2) 201-15, 2011.)
2. Ask students, What is the effect of light exposure on activity?
Answer: There is a strong correlation. When exposed to light, students were active.
3. Why does activity remain high in the evening even when there is a gradual decrease in stimulus?
Answer: Artificial light has made it possible for humans to remain active at night, long after the sun has
set. Scientists are currently exploring the impact that this has on human health.
4. What do you think is happening in the absence of light?
Answer: Students were physically inactive (sleeping) from about midnight to 6:00 a.m.
EXPLORE
Note: A sleep diary can help build toward understanding sleep and identify other questions to ask during the
Bright Schools competition after completion of the two Bright Schools lessons.
1. Ask students to plan a sleep diary that will help them develop their own 24-hour profile of the effect of
circadian stimulus on activity over time. Brainstorm with the class for information that should be kept as
part of the sleep diary. Information could include: the time they went to bed, the time they woke up,
whether or not they felt refreshed upon awakening, whether or not they needed an alarm clock to wake
up, when they started to feel sleepy, how many times they got up during the night (and the cause), what
time they stopped watching TV or using their phone, etc.
2. Have students create a data table to reflect the information that they will be collecting.
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Note: The National Sleep Foundation has a sample sleep diary that could be modified. The diary is
available at http://www.sleepforkids.org/pdf/SleepDiary.pdf or scan the QR code below. Use this as a
reference or guide, but allow data collection to be student-driven.
3. Collect data over the next 24 hours.
Note: To save time, collecting one night’s worth of data from multiple students (as we do here) is okay. An
even better approach would be for students to collect and analyze individual data over a longer period of
time.
4. Have students get in groups to analyze and interpret the data they collected. Discuss any patterns that
emerged. Discuss their sleeping habits. You may also want students to estimate the amount of sleep they
get per day/night during the week versus each day on a typical weekend.
Note: For students who have difficulty with math, provide a clock face that they can use to count the
number of hours of sleep.
5. Inform students that, on average, teenagers need 9.25 hours of sleep nightly (Mindell & Owen, 2003).
Ask students how the number of hours they are actually sleeping compares to the amount they should
be sleeping. How does it affect them? Answers will vary.
6. Students can calculate when they should be going to bed at night by accessing a Sleep Plan Calculator
from http://www.binfy.com/sleep-planner-calculator.php or by scanning the QR code below.
Based on the information they receive from the calculator, are they going to bed on time? Answers will
vary.
EXPLAIN
1. Brainstorm: What do you know about light? Example answers could include: made of waves, wakes me in
the morning, allows me to see, etc.
Note: It may be helpful to use a K-W-L Chart here (what a student knows, wants to know, and has learned
about a topic) to collect pre- and post-data and help address misconceptions and preconceptions. This
type of chart can also be useful to prepare students for research based on what they want to know.
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2. Show students the diagram below (Figure 2). Tell them this is how scientists diagram light. Ask students
what this diagram tells them about light.
Figure 2. The electromagnetic spectrum.
Ask students, Of these waves/types of electromagnetic radiation, which have more energy? Support your
answer. Answers should be x-ray or gamma ray. Example support: When we go to the dentist they put a
lead vest over our body to prevent the waves from damaging organs. More energy leads to damage.
After students have given answers, tell students that we cannot see most parts of the electromagnetic
spectrum (we can only see visible light). An example is radio waves when we listen to the FM radio. Tell
students that the electromagnetic spectrum is composed of many types of radiation, but we will just be
focusing on a small portion, visible light. Can you see where this portion exists on the diagram?
3. Have students use their finger to trace the wavelengths shown below. Which of these patterns of waves
have more energy? Have students explain their answer. Note: This could be done as a think-pair-share
exercise.
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Which of these lines is higher energy and which is lower? The spectrum diagram shows the wavelengths
of visible light as colors, which is how our sensory receptors interpret the wavelengths. With that in
mind, which of these lines is possibly red and which is blue? The top line represents blue light because it
has higher energy. The bottom line represents red and is lower energy.
Note: Color is not a property of light, but rather the way that sensory receptors interpret visible light
wavelengths. This is important to explain to students so they know that when referring to colors of
light, they are referring to wavelengths of light interpreted as color.
4. Have students read this Washington Post article, underlining key points that could answer the question
how do higher and lower energy visible light affect sleep?
http://www.washingtonpost.com/national/health-science/blue-light-from-electronics-disturbs-sleepespecially-for-teenagers/2014/08/29/3edd2726-27a7-11e4-958c-268a320a60ce_story.html
The circadian system is tuned to shorter wavelengths, therefore shorter wavelengths reduce the
production of melatonin at night.
Ask students, 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? Blue light can be helpful to
daytime alertness and functioning.
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5. Next, ask students to brainstorm different sources of light. What kinds of light are they receiving
throughout the day? Answers will vary, but some examples are sunlight, TV, computer screen, overhead
lights, full spectrum fluorescent lighting, etc.
Is all natural light beneficial? UV light in sunlight can cause sunburns and skin cancer.
6. Ask students to explain how they think a low energy wave could suppress melatonin production to the
same extent as a high-energy wave? Any wavelength can suppress melatonin production depending on
the amount received.
7. Explain that 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.
8. Have students test several different light bulbs with different lux readings using the light meter apps
(LuxMeter or EdenApp) 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.
Possible questions for students to consider prior to exploring:
A. Functional Lighting
1. Brainstorm in your small groups to list as many different sources of light as you can.
2. What type of lighting do you think would be best for a planetarium or a movie theater?
3. What type of lighting do you think would be best if you were designing a bedroom?
4. What type of lighting do you think would be best if you were designing a school?
5. How is light related to a building’s function?
B. Light Sources
1. Show students an incandescent standard light bulb, an energy-saving bulb (compact fluorescent),
and an LED light of the same wattage. Have students predict what will happen when they take a
reading with the light meter app. What is the advantage of an energy-saving bulb? Compare the lux
output for the three bulbs.
2. If possible, obtain a black light. Have students predict what will happen when they take a reading
with the light meter app.
3. If possible, obtain a plant grow light. Have students predict what will happen when they take a
reading with the light meter app.
C. Light Intensity
Have students take readings of a light bulb at intervals of every 100 cm. What happens to the
amount of light received as they move away from the light source?
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1. Ask students what factors of light relate to the quality of sleep they get.
There are several factors related to the quality of sleep: the type of light, timing of light received, and the
intensity. Timing of light is important because light at night can reduce production of melatonin. Shorter
wavelengths of light also reduce production of melatonin. And the more intense the light, the higher the
amount of light you are receiving. Depending on when you receive the higher amounts of light, it can
affect sleep. These three factors will be important as they proceed in their investigations.
ELABORATE
1. Have students plan an investigation to collect baseline data regarding the amount of light that they are
exposed to as they go throughout their school day.
For example, what percentage of the light they receive is from sunlight versus electric lighting?
2. Have students work in teams of three to four to develop a plan for collecting measurable data. Ideally,
each student group will develop a plan that is unique. You may want to suggest some of the options
listed below that students could employ for collecting data:
a. Students could use light meter apps to document variance in readings at different times of the
day or in different locations.
b. Students could record the size of their classroom(s) as well as the number, size, and location of
windows that allow light in. These data points will allow students to identify amount of natural
light they receive in the classroom. The information could be recorded in a data table and
supplemented with a sketch drawn to scale on graph paper.
c. Students could record the percentage of time their classes are spent with the lights on versus
with the lights off.
3. Allow students to carry out their investigation. Note: Observe safety protocols involved in conducting
these investigations.
EVALUATE
Evaluate student investigation designs from Elaborate section.
Have students analyze and interpret the data they collected. How does their data help to inform them about the
quality and/or quantity of light they are receiving? Have them make a claim regarding the quality/quantity of
light that they are receiving during the school day and defend their claim, data, and reasoning to their peers.
Answers will vary, but students should support their claim with both data used as evidence and scientific
reasoning related to circadian rhythms.
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Link to Bright Schools Competition (Extend)
Guide students in creating a question related to sleep and light or to school performance and light. Using the
student-collected data about light exposure at their school from this lesson, have students either propose an
experiment, create a model that would improve lighting conditions at school, or create an awareness campaign.
Find competition details here: http://brightschoolscompetition.org/.
Differentiated Instruction
Depending on the learner, some students may need a problem question and/or example procedures provided to
them to plan an investigation.
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Appendix
The pervasive glow of electronic devices may be an impediment to a good night’s sleep. That’s
particularly noticeable now, when families are adjusting to early wake-up times for school. Teenagers
can find it especially hard to get started in the morning. For nocturnal animals, it spurs activity. For
daytime species such as humans, melatonin signals that it’s time to sleep.
As lamps switch off in teens’ bedrooms across America, the lights from their computer screens,
smartphones and tablets often stay on throughout the night. These devices emit light of all colors, but it’s
the blues in particular that pose a danger to sleep. Blue light is especially good at preventing the release of
melatonin, a hormone associated with nighttime.
Ordinarily, the pineal gland, a pea-size organ in the brain, begins to release melatonin a couple of hours
before your regular bedtime. The hormone is no sleeping pill, but it does reduce alertness and make sleep
more inviting.
However, light — particularly of the blue variety — can keep the pineal gland from releasing
melatonin, thus warding off sleepiness. You don’t have to be staring directly at a television or
computer screen: If enough blue light hits the eye, the gland can stop releasing melatonin. So easing
into bed with a tablet or a laptop makes it harder to take a long snooze, especially for sleep-deprived
teenagers who are more vulnerable to the effects of light than adults.
During adolescence, the circadian rhythm shifts, and teens feel more awake later at night. Switching on a
TV show or video game just before bedtime will push off sleepiness even later even if they have to be up
by 6 a.m. to get to school on time.
The result? Drowsy students struggling to stay awake, despite the caffeinated drinks many kids now
consume.
“Teenagers have all the same risks of light exposure, but they are systematically sleep-deprived
because of how society works against their natural clocks,” said sleep researcher Steven Lockley of
Harvard Medical School. “Asking a teenager to get up at 7 a.m. is like asking me to get up at 4 a.m.”
In a 2014 poll, the National Sleep Foundation, an advocacy organization, polled parents, asking
them to estimate their children’s sleep. More than half said their 15-to-17-year-olds routinely get
seven hours or fewer hours of sleep. (The recommended amount for teens is 8 ½ to 10 hours.) In
addition, 68 percent of these teens were also said to keep an electronic device on all night – a
television, computer, video game or something similar.
Based on what parents reported, 45 percent of them were described as having excellent sleep
quality vs. 25 percent of those who sometimes left devices on.
“It is known that teenagers have trouble falling asleep early, and every teenager goes through
that,” said light researcher Mariana Figueiro of the Rensselaer Polytechnic Institute in Troy, N.Y.
Figueiro investigates how light affects human health, and her recent research focused on finding out
which electronics emit blue light intense enough to affect sleep. When comparing melatonin levels of
adults and teenagers looking at computer screens, she was astonished by the younger group’s light
sensitivity. Even when exposed to just one-tenth as much light as adults were, the teens actually
suppressed more melatonin than the older people.
In another experiment, she had adults use iPads at full brightness for two hours and measured their
melatonin levels with saliva samples. One hour of use didn’t significantly curtail melatonin release, but
two hours’ did.
So although teenagers may be particularly susceptible, we all should be aware that artificial light can
affect our circadian rhythms.
“The premise to remember is [that] all light after dusk is unnatural,” Lockley said. “All of us push our
sleep later than we actually would if we didn’t have electric light.”
A study from 2013 found that people who spent a week camping in the Rocky Mountains, exposed to
only natural light and no electronic devices, had their circadian clocks synchronized with the rise and fall
of the sun. Although there were only eight campers, they all reacted in the same way, whether they
considered themselves early birds or night owls.
So light serves as a cue, but how? It has long been known that the retina contains two types of
photoreceptors, or light sensors: rods and cones. The cones allow us to see colors, while the ultrasensitive rods are used for night vision, motion detection and peripheral vision. But surprisingly, neither of
them is the body’s primary tool for detecting light and darkness and synchronizing our circadian clocks.
There’s a third kind of sensor in our eyes, officially discovered in 2002. Called intrinsically photosensitive
retinal ganglion cells, or ipRGCs, these relatively crude sensors are unable to pick up on low levels of light
— from a dim night light, for example — but sluggishly signal light changes.
They are the body’s way of sending ambient light information to the master circadian clock, a huddle of
nerve cells in the brain. This clock makes the pineal gland start and stop the secretion of melatonin. The
ipRGCs are most sensitive to blue light — that’s why blue light is bad for your sleep.
To counteract the effects of tablets’ blue light, Figueiro and Lockley recommend a free app, F.lux, that
automatically warms up the colors on your various screens — more reds and yellows — at sunset and
returns them to normal at sunrise.
“The amount of light you need [in order] to see is lower than the amount of light you need to affect your
melatonin,” Figueiro said, which means that light-emitting screens can be used at night without disrupting
sleep cycles if you put some distance between your eyes and the device. In other words, place the tablet
farther away from your face than usual, or watch TV instead. Also, turning the brightness setting down on
laptops, tablets and phones should help.
But for teenagers, this doesn’t completely remedy the problem of early school start times. Lockley also
blames the early- morning sluggishness of many students on school start times that ignore their
changing body clock.
High schools in a handful of cities have shifted their start times to 8:30 a.m. or later. In a University of
Minnesota study whose final report was issued in February, researchers who surveyed about 9,000
students at eight high schools found that such a shift correlated with improvements in grades,
achievement tests, attendance rates and car accident rates.
In Virginia, Fairfax County has been considering delaying its high school start time until after 8
a.m. In Maryland, Montgomery County has discussed a change but has not decided on one yet.
Last week, the American Academy of Pediatrics issued a recommendation that middle and high schools
delay the start of classes to 8:30 a.m. or later. Pediatrician Judith Owens, the lead author of this policy
statement, said that later start times will help adolescents get the sleep they need and lower their risks
of obesity and depression.
“Sleep is important for learning, memory, brain development, health,” Lockley said. “We’re
systematically sleep- depriving kids when their brains are still developing, and you couldn’t
design a worse system for learning.”
Many Americans may believe early risers are more successful and that people can learn to live on little
sleep, Lockley said, but that notion is neither true nor healthy.
“There’s no training people to live without sleep,” Lockley said. “It’s like trying to train people to live
without food.”
Kim is a freelance science journalist in Philadelphia.
Article courtesy of The Washington Post, http://www.washingtonpost.com/national/health-science/bluelight-from-electronics-disturbs-sleep-especially-for-teenagers/2014/08/29/3edd2726-27a7-11e4-958c268a320a60ce_story.html