now browsing by category
Students learn about some animal adaptations for life in the snow by comparing features of pairs of similar animals that live in different environments. They explore their local area, searching for and learning to identify animal tracks in snow using a field guide. Using life-size stencils of selected animals from Alaska and other areas, students calculate the foot-load or weight-load of different animals and notice that animals inhabiting the snowiest environments tend to have lower foot-load values than those in less snowy environments. They experiment with the relationship between body weight, surface area, and depth of sinkage in snow by measuring how deep they sink in snow with and without snowshoes.
This set of activities includes many options; teachers can choose to do some or all of the activities according to students’ ages and interests and time available.
These activities complement “Feet, Float, and Physics: Exploring an animal adaptation to life in the snow,” an interactive online learning module for 6th grade and up available on the Our Winter World project website at: http://ourwinterworld.org/activity/. We encourage you to try it out with your students and share your feedback with us via the online comments form.
Snow and Living Things: Animals. 2020. Our Winter World website. http://ourwinterworld.org/snow-and-living-things/animals/
Feet, Float, and Physics: Exploring an animal adaptation to life in the snow. 2021. Our Winter World website. http://ourwinterworld.org/activity/
How have plants and animals adapted in your area? UA REACH Curriculum, Unit 13: Your Environment, Lesson 13 – Grade 6. 2015. University of Alaska K-12 Outreach. https://www.alaska.edu/k12reach/grade6year3.php
Folding Animal Track Pocket Card to download and print. Alaska Department of Fish and Game. https://www.adfg.alaska.gov/static/education/educators/pdfs/track_pocket_card.pdf
Why are my feet so big? Lesson plan. 2020. Alaska Department of Fish and Game. (Contact Fairbanks Office for information)
Materials necessary for activity.
Our Winter World: Animal adaptations to living in the North (PowerPoint presentation file on flash drive in materials kit)
● Animal Tracks of Alaska field guides (4)
● measuring tape (dual metric/imperial scale) (2)
● clear 1 inch x 1 inch gridded acrylic boards (4)
● dry erase markers (1 set, assorted)
● dry erase cleaning fluid (1 bottle)
● Set of animal track stencils (assorted)
● graph paper (choice of 1 inch x 1 inch grid or 1 cm x 1 cm grid)
● snowshoes (1 pair)
1. Introduce animal adaptations to northern environments
Read instructions on first slide of PowerPoint presentation, then display PowerPoint presentation, moving animal photos to the appropriate columns according to student input. (If easier, you may also print the presentation, cut out the animal pictures, and ask students to sort them manually according to each characteristic, revealing the animals’ geographic range after each sorting task.)
Tell the students that the rest of the activities in this lesson will focus on animal feet. What did they notice about the size of more northerly animals’ feet in comparison to similar animals from more southern/less snowy locations? Animals inhabiting very snowy environment tend to have larger feet compared to their body size and weight as compared with animals inhabiting less snowy environments. Ask for suggestions as to how this might help animals succeed in the north, and in the snow in particular? (Larger feet relative to body weight results in lower foot-load or weight-load, which means that the animal exerts less pressure on the surface of the snow than would a heavier animal or one with smaller feet. This helps these animals “float” on top of the snow better, making it easier and less energy-intensive for them to travel from place to place in winter.)
2. Outdoor exploration: Identifying and measuring animal tracks
Ask students to share stories about what animals they have seen lately and about different types of animal tracks they see in the area and can identify. Guide them in browsing though the animal track field guides, coaching them to interpret range maps, gait patterns, dimensions and labels, and any differences between front and hind feet or juvenile and adult tracks.
Optional: Allow students to take photographs one or two pages of the field guide with their phones so that they can refer to the pictures in the field. OR, if time allows, make photocopies of selected pages of the field guide for tracks that you are likely to find near your school and create half-sheet sized laminated track cards that can be taken out in the field.
Go outside to explore and find animal tracks, identifying what type of animal made the tracks when possible. Note how deep the animal tracks are in the snow, and estimate how recent the tracks are based on the most recent snowfall event.
Optional: Try tracing a good track or set of tracks using the clear acrylic gridded board. To do this, lay the board, grid side down, on top of the track. If the snow is very new and soft, the board might sink in and ruin the track. If it stays in place and you can see the track through the clear board, however, use a dry erase marker to trace the outline of the track on the plain acrylic (plexiglass) side of the board. Take the board inside and set it down so that the plastic grid is face up. Count the number of 1 inch squares that fall within the track outline that you drew. One method that is helpful for finding the total area of the track is to count every square that is at least half inside the outline of the track. Don’t count the squares that are less than half inside the track outline. The total number of squares that you count will add up to the area of the track in square inches.
This activity may be done in conjunction with the snow pit study or as a separate lesson. Students use a snow sampling tool of established volume to explore snow density and snow-water-equivalent (SWE), the amount of water that is contained within a given volume of snow. Older students may calculate density and SWE values, whereas younger students will learn based on observation and comparison of different snow samples.
In addition to gaining an introduction or applied context for the concept of density, students will gain an appreciation for the importance of snow as a water source.
What is SWE? Snow Water Equivalent. 2021. MissoulaAvalanche.org. https://missoulaavalanche.org/2021/01/what-is-swe-snow-water-equivalent/
What is Snow Water Equivalent? No Date. Natural Resources Conservation Service, U.S. Department of Agriculture (USDA) https://www.nrcs.usda.gov/wps/portal/nrcs/detail/null/?cid=nrcseprd1314833#:~:text=Snow%20Water%20Equivalent%2C%20or%20SWE,the%20snowpack%20when%20it%20melts.
Snow Density. Avalanche Encyclopedia. 2021. American Avalanche Association and National Avalanche Center. https://avalanche.org/avalanche-encyclopedia/#density-snow-1
Included in kits unless otherwise noted
● snow sampling tools (black PVC tubes with handles) (2)
● foam stands for sampling tools (2)
● square wooden rulers for sampling tubes (2)
● large metal spatulas (2) – from snow pit study materials
● extendable utility shovels (2) – from snow pit study materials
● Snow density sampling how-to video clip LINKED HERE
1. Activity set up
At least twenty minutes before starting the activity, place the snow sampling tubes and spatulas outdoors to cool down, so that they don’t melt the snow when they come in contact with it during the sampling process.
There are only two sets of sampling tubes. If you would like more students to be able to participate in the sampling activity at the same time, the activity can be done by collecting snow in other types of containers of known volume (e.g. plastic containers provided in the kit) with some modification in procedures. To be able to compare results from different locations, all students should use the same type of container and follow the same procedures.
2. Activity introduction and demonstration
If students have already completed the snow pit study, they will have noticed that there are differences in snow grain size and shape, how much the snow grains stick together, how much space there is in between the snow grains, and how hard or compacted the snow is among different snowpack layers. One characteristic of snow that scientists measure when doing a snow pit study is the density of the snow layers and the overall or bulk density of the snow at that location.
If students have already been exposed to the concept of density in math or science, ask a student to refresh everyone’s memory of what it means and how it is calculated.
- Density is equal to mass (usually measured in grams or kilograms) divided by volume (usually in cubic centimeters or cubic feet).
- If you have two objects of identical size and shape and one feels “heavier” than the other, it is the denser of the two objects. (It contains more mass or material within the same volume.)
You might also ask guiding questions to find out if students have an intuitive or experiential understanding of what density means and how it is different from but related to weight.
Do students have any ideas about why someone would want to know about how dense the snow is? They are not expected to have answers in advance, but they might suggest implications for snow stability/avalanche risk/ “post-holing” in snow; determining which snow is best to melt for water; or other ideas from personal experience.
Another way we can think about density of snow is to think in terms of how much water it contains. Snow is made up of ice particles and air, so snow with more ice and less air is more dense than snow with less ice and more air. By collecting a known volume of snow and letting it melt, we can measure how much water it contained, which is related to its density.
3. Activity procedures
If available, show the video clip of UAF snow scientist Charlie Parr demonstrating how to collect snow samples using the density sampling tool.
Note that only two students will be able to collect samples at a time if using the snow sampling tools. Designate two students to take the samples. Distinguish the tools by writing each students’ initials on a piece of tape and affixing the tape to the wooden handles of the tools. You might suggest that the students collect samples from different layers in the snowpack or from different locations.
- Use the shovel to cut vertically into the snowpack and remove snow from the area where you want to collect your sample. (See first snow pit study video clip for a demonstration.) Expose a vertical wall of snow at least 0.5 meters wide so that you can access it. Use a whisk broom or a gloved hand to brush loose snow from the exposed vertical surface so that you can see the locations of the different snow layers.
- Decide which layer you want to sample. The layer must be at least as thick as the diameter of the tool opening. If it is not thick enough, choose a different layer.
- Insert the tool.
- If you choose to sample the top layer of snow, hold the wooden handle and insert the open end of the tool horizontally into the layer exposed in the face of the snow wall, being sure to keep it horizontal. Push it into the snow gently but firmly until the bottom of the black cylinder is flush with the face of the snow wall (with just the handle sticking out).
- If you choose to sample a layer that is lower in the snowpack, use the shovel or metal spatula to gently remove (by scraping away) the upper layer(s) of snow. Once you have removed the snow above the layer that you would like to sample, repeat the process described in step 3.a.
- Use the large metal spatula to cut down vertically into the snow at approximately the location where you expect the open end of the tube to be located. (It might be helpful to use a ruler or tape measure to find the approximate location by measuring horizontally 13 centimeters back from the exposed snow wall.) Move the spatula around or cut down from the top again to try to find the position at which the spatula will cover the open end of the tube. Be sure not to push the spatula toward the tube opening, as this will push more snow into the tube, compacting it, which will affect the results.
The spatula can be done by the student who is still holding the sampling tube or by another student if more convenient.
- When the spatula is touching the open end of the tube and covering the opening, gently and slowly pull the tube out of the snow horizontally, being sure that the blade of the spatula remains fully covering the opening of the tube the whole time.
- Once the tube has been extracted from the snow, slowly turn it to the upright position, keeping the spatula blade over the opening.
- Once the tube is in the upright position and being gripped by the handle, the spatula can be removed, and the sample should be carried inside, being careful not to spill any of the sample.
- In the classroom, insert the handle of the tube into the foam stand so that it remains upright while the snow melts.
- Place the tools in their stands on a stable surface close to a heat source, if possible, to speed up melting.
- When the snow in the tube has completely melted, insert the square wooden ruler, with the zero mark down, vertically into the center of the tube so that it touches the bottom. Then remove it. The part of the ruler that was submerged in the water will appear darker.
- Measure how deep the water was by referring to the darker colored, wet portion of the ruler.
4. Calculating density and snow-water equivalent
This portion is optional and is suitable for students who are more advanced in math, including geometry.
- Calculate the volume of the cylinder, which is the volume of the snow sample if collected properly.
Volume of the cylinder in cm3 = pi x radius of the cylinder squared x height of the cylinder
Vcylinder = π x r2 x hcylinder
The number pi (π) can be abbreviated as 3.14
V = volume, r = radius, h = height
- Calculate the volume of liquid water contained in the snow sample.
Volume of water in the cylinder in cm3 = pi x radius of the cylinder squared x height of the water in the cylinder
Vwater= π x r2 x hwater
The number pi (π) can be abbreviated as 3.14
V = volume, r = radius, h = height
- Determine the mass of the water in the cylinder.
Water has a known density of 1 gram per 1 cubic centimeter (1 g/cm3). Therefore:
Mass of water in the cylinder = volume of water in the cylinder times the density of water.
mwater= Vwater x 1 g/cm3
m = mass, V = volume, 1 g/cm3 = density of water
Density is represented by the symbol ρ (Greek letter rho)
- Determine the density of the original snow sample.
Density of the original snow sample = Mass of water in the cylinder divided by volume of the cylinder.
ρ snow = mwater ÷ Vcylinder
ρ = density, m = mass, V = volume
5. Comparing and discussing results
Compare the depth of water that resulted from the two different samples. Was there more water in one sample than another? Were the samples taken from the same snowpack layer or a different snowpack layer? If from different layers, which layer contained more water?
We can infer from the amounts of water that each sample contained whether one snow sample was more dense than the other. Which sample was more dense?
6. The importance of water from snow
References to help connect the activity content to critical freshwater resources from snow:
Importance of snow. 2020. Our Winter World website. http://ourwinterworld.org/importance-of-snow/
Importance of snow: Supplying Water. 2020. Our Winter World website. http://ourwinterworld.org/importance-of-snow/supplying-water/
Snow Program Overview. National Water and Climate Center, Natural Resources Conservation Service, U.S. Department of Agriculture (USDA). https://www.nrcs.usda.gov/wps/portal/wcc/home/aboutUs/snowProgramOverview/
Program History. National Water and Climate Center, Natural Resources Conservation Service, U.S. Department of Agriculture (USDA). https://www.nrcs.usda.gov/wps/portal/wcc/home/aboutUs/programHistory/
This activity reinforces the fact that snow crystals (which we often call snowflakes) have hexagonal (six-sided) symmetry. Students fold round paper and cut out their own six-sided snowflake designs.
Recommended age/grade range: all ages!
Time required: 20 minutes
Ken Libbrecht – Snowflake Science: A Snowflake Primer – http://www.snowcrystals.com/science/science.html
Ken Libbrecht – Types of Snowflakes chart – http://www.snowcrystals.com/guide/snowtypes4.jpg
Ken Libbrecht – Snowflake Photographs – http://www.snowcrystals.com/photos/photos.html
Ken Libbrecht – Designer Snowflakes – http://www.snowcrystals.com/designer/designer.html
Included in kits unless otherwise noted
● Circular white paper
● Snow crystal types charts – laminated
● Scissors must be provided by the school
1. Activity set up
Optional: You may choose to cut out a couple of snow crystals to show as examples or help provide ideas.
2. Introduction: Hexagonal symmetry
When we see these crystals falling from the sky, we usually call them snowflakes. Snowflakes can be individual snow crystals, or they can be clumps of snow crystals stuck together.
Snow crystals can be different shapes and sizes, but they all have six sides or arms. (Sometimes when we find them they are broken, so we can’t see all of the arms.)
Look at snow crystal types chart:
Practice finding and counting 6 sides & 6 arms of crystals depicted in the chart.
Introduce or remind students of the concept of symmetry. Because snow crystals have six identical sides/arms and an individual crystal looks the same no matter which side or arm is “up,” we say that snow crystals have hexagonal symmetry. (Show the shape of a hexagon.)
3. Paper snowflake activity
Today we’ll be cutting out our own hexagonally symmetrical snow crystals.
Has anyone made a paper snowflake before? Let’s first look at some examples found online.
Optional: Look at paper snowflakes online or take a walking field trip to view paper snowflake decorations. Are there some designs that couldn’t actually be found in nature? Which ones? (Paper snowflake crafts are sometimes made with four- or eight-sides. These may be pretty, but snow crystals in nature only have six sides or arms. (Sometimes they can appear to be twelve-sided/twelve-armed when two snow crystals stick together or “aggregate” and then continue to grow as one….but their symmetry is always a multiple of six.)
Display examples and coach kids through cutting out snow crystals.
Allow students to take their snow crystals home or use them to decorate windows or bulletin boards at school.
For students who want a challenge, show them (or encourage them to find online) photographs of specific snow crystal shapes and challenge them to create a paper snowflake that looks like the example.
Many different examples of photographs of real snow crystals can be found on Ken Libbrecht’s snowcrystals.com website.
Step 1: use circular piece of paper
Step 2: Fold circle in half
Step 3: fold the halved circle into thirds
Step 4: figure out how you want to cut your snowflake and cut your lines
Step 5: Unfold your snowflake and see what you created!
If you run out of circular paper, see the following instructions for how to make six-sided snowflakes out of 8.5 x 11” paper:
KarenHC, November 30, 2015. Instructions for making paper snowflakes – an easy tutorial. When Life is Good. http://www.whenlifeisgood.com/instructions-for-making-paper-snowflakes-an-easy-tutorial/ [Retrieved 8/22/2021]
Students make plaster casts of animal tracks found outside or create plaster imprints of animal track replicas. They gain practice observing the natural world closely, and create a memento they can keep without removing any objects from the natural world.
How to make plaster casts of an animal track. 2011. MyNatureApps. https://www.youtube.com/watch?v=Y4WTmgo4zeA
Cabrera, Kim A. 2001-2007. Plaster Track Casting Procedure. Beartracker.com. https://www.michigan.gov/documents/dnr/Track_casting_382484_7.pdf
Save Animal Tracks as Plaster Casts. https://www.startwithabook.org/content/pdfs/tracksplastercast.pdf
Mangor, Jodie. 2021. How to make a plaster cast of animal tracks in the snow. Scout Life. Boy Scouts of America. https://scoutlife.org/hobbies-projects/funstuff/151633/make-a-plaster-cast-of-animal-tracks-in-the-snow/
Included in kits unless otherwise noted
● Plaster of Paris (2-4 x 4 lb. containers)
● Jumbo craft sticks for stirring/mixing plaster
● Gallon size Ziplock bags for mixing plaster and water
● 1-2” wide strips of cardstock or manila folder material for forming a ring or collar around the track to contain the plaster
● clothespin or paperclip to secure the cardstock/paper ring
● Spray bottle
● School provides water for mixing with plaster and for use in spray bottle to set the track in snow before pouring plaster. 32 oz. Nalgene water bottle provided in kit should hold enough water for a couple of smaller tracks; a moose or bear track might require the whole bottle.
Refer to instructions in reference materials listed above. Note that different sources have different opinions and preferences for materials and methods. Try an approach that appeals to you! One thing to note is that if you are making plaster tracks in snow, it is worth lightly spraying the track with a fine spray of cold water before adding the plaster to help set the track. Also, mix some snow in with the water when mixing your plaster so that the plaster mixture doesn’t melt the track.
In case you aren’t able to find any good tracks to cast outdoors, you can make negative track imprints using the flexible track replicas provided in your kit. Your kit will contain either a) two caribou tracks and two wolf tracks or b) two wolverine tracks and two snowshoe hare tracks.
Follow these steps to make negative impressions of the replica tracks provided:
- Use the paper bowls provided to mix individual portions of plaster and water. A mixture of two parts plaster to one part water is generally recommended.
- Fill the bowl about two thirds full with plaster-water mixture and continue to stir using a craft stick.
- When your plaster and water mixture is a good consistency (like thick pancake batter), smooth the top of it with a craft stick.
- If you have access to cooking spray, you might choose to lightly spray the surface of the track replica before inserting it into the plaster.
- Then, firmly press the track replica face-down into the bowl of plaster. Allow it to sit, undisturbed, for approximately twenty minutes.
- After twenty-five minutes, lightly touch the plaster with your finger to test how dry it is. If it is fairly dry and stiff, attempt to remove the track replica from the plaster.
- Your result should be an imprint of the track – just like what you might find in the snow or mud if you found an animal track outdoors.
- Ideally there will be enough bowls that each student can make an imprint and take a bowl home; there is no need to remove the plaster from the bowl. They may choose to decorate the final product with paint or glitter or to add their initials, the date, and the name of the animal whose track they have cast.
Students conduct a simple experiment to investigate reflection and absorption of visible light by dark and light materials. They learn that the term albedo refers to the ratio of how much incoming light is reflected by a substance and explore the albedo values of different types of surfaces on Earth. Based on the results of the experiment, they make inferences about the important role that snow plays in regulating Earth’s climate.
Importance of snow: Cooling the planet. 2020. Our Winter World website. http://ourwinterworld.org/importance-of-snow/
Snow science: Optical properties of snow. 2020. Our Winter World website. http://ourwinterworld.org/snow-science/properties-of-snow/#optical-properties
Changing Albedo Values. My NASA Data. https://mynasadata.larc.nasa.gov/basic-page/changing-albedo-values. Includes links to:
- Earth’s Energy Budget Includes Albedo (Why does the Sun Matter for Earth’s Energy Budget? video)
- When do albedo values change? (Climate Bits: Albedo video)
- Why does NASA study albedo? (Global temperature anomalies from 1880 to 2018 video)
Albedo – Terrestrial Albedo. 09.03.2021. Wikipedia. https://en.wikipedia.org/w/index.php?title=Albedo&oldid=1042141005
Earth’s Energy Balance (online interactive simulation). 2021. University Corporation for Atmospheric Research (UCAR) Center for Science Education. https://scied.ucar.edu/interactive/earths-energy-balance
Included in kits unless otherwise noted
Kits include enough materials so that four groups of students can do the experiment at the same time.
● Black felt pockets (4)
● White felt pockets (4)
● Dial stem thermometers (8)
● Clamp on lamps with reflector shades (4)
● 60 Watt Incandescent light bulbs (4)
● Schools might need to provide extension cords and/or power strips for lamps.
1. Experiment set up
Set up four stations. For each station, you will need a desk, table, or other flat surface; 1 black felt pocket; 1 white felt pocket; and 1 clamp lamp with light bulb.
Lamps should be positioned so that they shed light on the surface below them, upon which the two felt pockets will be placed side by side. The lamps should be centered over the surface so that each pocket receives the same amount and intensity of light. If there are no good options for affixing the clamp lights above desk/table height, you can clip them to the edge of the desk and set up the felt pockets on the seat of a chair underneath.
Felt pockets should be oriented so that the thermometer dial can be read easily while the thermometer stem is inserted into the pockets.
Check to make sure the two thermometers at each station read within a degree or two of each other. If they don’t, refer to the instructions on the packaging to calibrate them so that they start at the same temperature.
2. Experiment introduction and hypothesis development
Introduce what the experiment will entail without presenting too much information about the underlying science.
Ask students to develop a hypothesis based on their everyday life experience as to whether and in which direction they think that the temperatures will change (go up, go down, or don’t change) and whether and how the temperature changes will be different between the black and white felt pockets (e.g. one will go up, one will go down; both will go up but the black one more so than the white one, etc.).
Ask students to write down their hypotheses in a notebook or data sheet and to including their rationale, whether based on life experience, knowledge of underlying scientific concepts, or intuition.
3. Experiment steps
Students at each station should follow these steps in sequence:
1. Before turning the lights on, insert a thermometer into each pocket (one black, one white) so that the dial is facing them and the stem is fully covered by the felt. Ensure that the thermometers are placed in such a way that the lamp is centered over them, providing an equal amount of light to each pocket.
2. Read the initial temperature of both thermometers and record them in a notebook or data sheet.
3. Turn on the light. Without touching the materials, watch the thermometers for changes in temperatures.
4. After five minutes, check the temperatures, being sure not to touch the thermometers or remove them from the pockets. Record the temperatures in a notebook or data sheet, being careful to note which temperature is for the black felt pocket and which is for the white felt pocket.
5. If there is a substantial temperature difference between the two thermometers after five minutes, you can end the experiment. However, if there has only been a small change in temperature and/or if the temperature of one or both thermometers seems to be continuing to change rapidly, wait another three to five minutes and record the temperatures again.
3. Share and discuss results
Ask each group to calculate how much the temperature of the white pocket and the black pocket changed during the experiment by subtracting the starting temperature from the ending temperature for each.
Compile results from all groups by having a representative of each group enter their temperatures in a whole class chart (e.g. created by the teacher on a white board) or by sharing aloud the starting and ending temperatures that they recorded for the white and black pockets. Note any discrepancies in results and check to find out if everyone followed the same experimental protocols.
Did the results support or conflict with their hypotheses? If so, do they have any thoughts about what might account for the results that they had not considered in developing their hypotheses?
If they haven’t already done so, ask students to share examples from their life experience that relate to the experiment. For example, if they have ever worn black or dark clothing versus white or light-colored clothing on a hot, sunny day, which color of clothing made them feel warmer? Has anyone had the experience of walking barefoot on black asphalt or lighter colored surfaces?
4. Connecting scientific concepts: Explaining absorption and reflection
Refer to background/reference information.
Light is either reflected or absorbed by an object or substance.
The word albedo refers to how much of the incoming light that an object receives is reflected by that object. More reflective objects have higher albedo values, and less reflective objects have lower albedo values.
Albedo values range from 0 to 1. An object that absorbs all incoming light and reflects none of it has an albedo value of 0. An object that reflects all incoming light and absorbs none of it has an albedo value of 1.
5. Applying what we’ve learned: Albedo, snow, and Earth’s climate
Display an aerial photograph or photograph of the Earth from space and notice the different colors of Earth surfaces. Which areas would the students expect to have high albedo values and which would have low albedo values?
6. Optional extension for advanced learners
A. Earth’s Energy Budget
Earth’s albedo is an important part of Earth’s energy budget, which describes the net amount of energy absorbed by the Earth based on its incoming energy and outgoing energy flows. Earth’s energy budget determines the temperature of the Earth.
This online interactive from UCAR Center for Science Education allows you to manipulate amount and brightness of incoming solar energy and the albedo of Earth’s surface and see how changes to those values affect Earth’s temperature: https://scied.ucar.edu/interactive/earths-energy-balance
B. The electromagnetic spectrum and visible light
NASA Science. 2021. Introduction to the Electromagnetic Spectrum (video). National Aeronautics and Space Administration (NASA). https://science.nasa.gov/ems/01_intro
NASA Science. 2021. Visible Light (video). National Aeronautics and Space Administration (NASA). https://science.nasa.gov/ems/09_visiblelight
Butcher, G., Mottar, J., Parkinson, C.L., and Wollack, E.J. 2016. Tour of the Electromagnetic Spectrum. National Aeronautics and Space Administration (NASA). https://smd-prod.s3.amazonaws.com/science-pink/s3fs-public/atoms/files/Tour-of-the-EMS-TAGGED-v7_0.pdf