Fellow name: Michael Hartinger
Title of Lesson: Why live on Earth?
School: Culver City High School
Grade Level: 9
Subject(s): Earth Science
This lesson will be used to introduce students to the electromagnetic spectrum and how the Sun transfers energy to the Earth through electromagnetic radiation. Topics will include the different types of electromagnetic radiation, the amount of energy available in electromagnetic radiation from the Sun, and how different types of radiation are absorbed/reflected/transmitted. In the activity, students examine how effective different chemicals (sunscreens, shampoos, hand-lotions) are in blocking UV radiation, using UV beads.
In what way is your lesson/activity inquiry-based?
Students will engage in an activity that allows them to study how effective different chemicals are in blocking ultraviolet radiation.
Cost to implement
After this lesson, students should be able to:
*Define the ozone layer and electromagnetic radiation
*List the types of electromagnetic radiation
*Describe how the Sun's electromagnetic radiation is affected by Earth's atmosphere
*List different ways that humans use the Sun's electromagnetic radiation that reaches the Earth's surface
Introduction / Motivation
Below is the material that I introduced to students in a Powerpoint before they did their activity. During the Powerpoint, I demonstrated how microwaves, an invisible part of the electromagnetic spectrum, can be blocked.
Did you know that the Sun is more than a million times larger than the Earth? Not only is the sun large in size, but it contains nearly all of the mass in our solar system and is the largest source of energy. This is true even at Earth, which is 93 million miles away. This isn't too surprising if you consider that the amount of energy the sun releases is, on average, equivalent to 100 billion tons of TNT exploding every second!
Radiation is a way of transferring energy through space from one location to a different location. The Sun transfers energy to the Earth through electromagnetic radiation, which includes visible light. Did you know that visible light is only one type of electromagnetic radiation? There are many types of electromagnetic radiation, which are invisible to us: They include radio waves, microwaves, infrared, ultraviolet, x-rays, and gamma rays. Together, they make up what's known as the electromagnetic spectrum.
The Sun is an extremely important source of energy at Earth's surface. Much of the energy used by society is driven either directly or indirectly by the electromagnetic radiation from the Sun that reaches the Earth's surface. The energy contained in the electromagnetic radiation that reaches the Earth is enormous. The energy delivered to one square meter at Earth during the day is enough to power a typical American household!
So where is all this radiation? The human eye can only sense the visible part of the spectrum. The rest is invisible, but you can still sense it using other detectors - for example, cell phones.
Demo with cell phone – put the cell phone on speaker and have someone call it, or call voice mail, so the students can hear the audio from the cell phone. Then place the cell phone in a small Faraday cage, which blocks the microwaves. The students should hear the audio on the cell phone cut off when it loses signal. A Faraday cage can be created by making a small pocket-shaped container with an inner layer of duct tape and an outer layer of tin foil – the container should be able to close in such a way that the cell phone isn't touching the tin foil and the tin foil has no gaps in it – one large, continuous piece of tin foil should be used for best results.
The Earth's atmosphere protects us from dangerous electromagnetic radiation. Have you ever taken steps to protect yourself against some forms of electromagnetic radiation? (lead apron when having a medical/dental x-ray, sunblock at the beach). You may be aware of the hazards associated with ultraviolet radiation. Fortunately, the ozone layer in the Earth's atmosphere prevents much of the Sun's ultraviolet radiation from reaching the surface by absorbing it. Other, higher energy forms of electromagnetic radiation are even more dangerous, such as x-rays and gamma rays. The Earth's atmosphere blocks nearly all of these types of radiation from hitting the Earth's surface. In fact, only about 55% of the Sun's electromagnetic radiation reaches the Earth's surface – the rest is reflected or absorbed by the atmosphere.
The Earth's atmosphere provides us with protection from hazardous radiation from the Sun. However, a significant amount of energy reaches the Earth's surface in the form of visible light and some infrared and ultraviolet radiation. This energy can then be used by plants and animals. It is also used to directly and indirectly power human technology. This balance of protection while still allowing ample energy to reach the surface makes the Earth hospitable to many different forms of life. No wonder we live here!
In this activity, you will see the effects of different types of electromagnetic radiation, using special detectors for each type. You will learn about several materials that block certain types of electromagnetic radiation, but not others, just like our atmosphere.
The activity will familiarize students with the concept of invisible electromagnetic radiation and the shielding effects of different materials.
The students will divide into groups of four or five and receive several color-changing ultraviolet beads (available through Lakeshore Learning Supplies and other teaching supply vendors), and several transparent, plastic sandwich bags. Several unmarked chemicals will also be made available to the entire class to test. The chemicals should have different levels of ultraviolet blocking capability (e.g. sunblock, shampoo, hand lotion).
The groups will test how well each chemical blocks ultraviolet light in the following way.
1) Go outside in sunlight.
2) Spread one chemical thinly on a sandwich bag and place a bead inside the bag. Place another bead inside a sandwich bag with no chemical.
3) Place the two bags next to each other and record any differences in color between the beads. The lighter the color of the bead in the bag with the chemical, the better that chemical's ability to block ultraviolet light.
Each student in the group should be involved in the activity, either by recording the data, spreading the chemicals, or collecting and assembling the materials. A handout may be used to guide the students through the activity, or, for more advanced classes, the students may want to try to figure out how best to test the chemicals on their own.
Each group will need:
*Several color changing, ultraviolet beads (at least 2, but more is better in case any chemicals get on the beads, or if more than one chemical is tested at the same time).
*5-10 transparent, plastic sandwich bags
*something to record observations
To share with the entire class:
*Chemicals to test – the students shouldn't know what they are. Sunblock, shampoo, and hand lotion bottles with the labels removed are some examples.
*Paper towels for the students to wipe their hands after handling the chemicals.
*The students should be aware that the chemicals are not hazardous as long as they are kept out of eyes/mouth.
In the lesson and activity, students learned how the Earth's atmosphere transmits enough electromagnetic radiation to support life while blocking much of the most hazardous forms of radiation. The situation is not the same on Venus and Mars, Earth's two closest neighbors in the solar system. Venus's atmosphere blocks a lot of harmful radiation from the Sun, but traps too much infrared radiation, making the surface incredibly hot – the atmosphere is also too thick to support life as we know it. The Martian atmosphere is too thin, and lets in too much harmful radiation from the Sun – any manned mission to Mars would need to account for this.
The Sun's energy is available at many other planets and at the Earth's moon and other moons. However, the Earth is special because it has a thick atmosphere that shields the Earth from dangerous radiation from the Sun, while allowing enough energy to get through to support life and power technology.
Is this lesson based upon or modified from existing materials? If yes, please specify source(s) and explain how related:
Bruton, Sheila and Feye Ong. Science Content Standards for California Public Schools. Sacramento, CA: California Department of Education, 2000.
Earth's Atmosphere. Last Updated April 10, 2009. NASA. Accessed August 2, 2009. http://www.nasa.gov/audience/forstudents/9-12/features/912_liftoff_atm.html
Earth Radiation Budget. Last Updated April 23, 1998. Environmental Science, Rutgers, The University of New Jersey. Accessed August 2, 2009. http://marine.rutgers.edu/mrs/education/class/yuri/erb.html
Solar System Exploration: Planets: Venus. Last Updated October 27, 2009. NASA. Accessed November 18, 2009. http://solarsystem.nasa.gov/planets/profile.cfm?Object=Venus
Solar System Exploration: Planets: Mercury. Last Updated October 22, 2009. NASA. Accessed November 18, 2009. http://solarsystem.nasa.gov/planets/profile.cfm?Object=Mercury
Vermas, Wimm. Photosynthesis. Last Updated June 12, 2007. College of Liberal Arts and Sciences, Arizona State University. Accessed August 2, 2009. http://photoscience.la.asu.edu/photosyn/education/photointro.html
Williams, David. Sun Fact Sheet. Last Updated September 1, 2004. Goddard Space Flight Center, NASA. Accessed August 2, 2009.
*Handout for students to record observations in activity and answer questions
*Handout of Powerpoint for students to follow along and take notes.
*Powerpoint for introduction and closure
List CA Science Standards addressed
Science: California Earth Science 4b – Students know the fate of incoming solar radiation in terms of reflection, absorption, and photosynthesis.
Science: California Earth Science 8b – Students know the location of the ozone layer in the upper atmosphere, its role in absorbing ultraviolet radiation, and the way in which this layer varies naturally and in response to human activities.
Lesson Implementation Comments
How did the lesson or elements of the lesson work as desired?
Based on responses to questions on the activity handout, most students understood the concept that ultraviolet light could be blocked by varying degrees by different chemicals – they also remembered that the ozone layer is the part of Earth's atmosphere that blocks ultraviolet light when asked during the lesson closure. The demo with the cell phone and Faraday cage also worked as desired, generating lots of questions and helping to dispel some misconceptions and get across the concept of invisible radiation.
How did the lesson or elements of the lesson not work as desired?
The material in the lecture (as implemented in the Powerpoint) and activity could be raised to a higher level of difficulty and include more information if the lesson is extended to two days. This would be desirable in future implementations to challenge students and more fully address the California content standards.
What needs to be done or was already done to revise the lesson to make it more effective?
*Extend the lesson to two days and raise the difficulty level/include more detailed information.