Electromagnetic Waves: How Do Sunglasses Work?
What happens to light waves when they pass through sunglasses?Copyright 2007 Hamed Saber, Wikimedia Commons CC BY-SA 2.0 https://commons.wikimedia.org/wiki/File:B%26W_girl_portrait_with_sunglasses.jpg
Students learn about the scientific and mathematical concepts around electromagnetic light properties that enable the engineering of sunglasses for eye protection. They compare and contrast tinted and polarized lenses as well as learn about light intensity and how different mediums reduce the intensities of various electromagnetic radiation wavelengths. Through a PowerPoint® presentation, students learn about light polarization, transmission, reflection, intensity, attenuation, and Malus’ law. A demo using two slinky springs helps to illustrate wave disturbances and different-direction polarizations. As a mini-activity, students manipulate slide-mounted polarizing filters to alter light intensity and see how polarization by transmission works. Students use the Malus’ law equation to calculate the transmitted light intensity and learn about Brewster’s angle. Two math problem student handouts are provided. Students also brainstorm ideas on how sunglasses could be designed and improved, which prepares them for the associated hands-on design/build activity.
Engineers begin design challenges by learning about relevant science and math concepts in order to fully understand the problem. For instance, engineers are currently trying to broaden the telecommunications spectrum and increase bandwidth to accommodate the rise in data streaming applications. The plan is to add frequencies in the 28–64 GHz range, which are not yet used in data streaming because of some limitations in their wave characteristics. The millimeter wave, as waves with this frequency are called, is prone to large attenuation (reduction in power) as it travels through walls and even human bodies. It also has a very small cell coverage area, which increases the need for antennas and cellular stations. Similar to how engineers are investigating and testing to learn more about radio/microwaves to accomplish this task, through this lesson, students learn about light properties to help them design and refine new types of sunglasses in the associated activity.
After this lesson, students should be able to:
- Calculate the light intensity when two polarizing films are used.
- Compare and contrast tinted and polarized glass.
- Evaluate light attenuation through different mediums.