I begin this lesson by reminding students that engineers design many devices that use different types of electromagnetic waves, including x-rays, microwaves and radio waves. Although they may not realize it, students interact with many of these waves and their applications on a daily basis. Lighting engineers focus on the visible spectrum of electromagnetic waves, and design creative lighting systems for both small and large applications.
In our previous lesson, we learned that light is an electromagnetic wave, and that visible light is the only part of the electromagnetic spectrum that we can usually see (without any special equipment).
Today students use their simple spectroscopes to discover that what we think of as white light is actually a combination of many different colors. When all these colors are combined together, the light appears white to our eyes. But, actually, different sources of light give off different combinations, or spectrum, of light.
Since light has many different wavelengths within it, these different wavelengths diffract at different angles. And, since different wavelengths produce different colors, separating the wavelengths means that the colors are separated, so we can see all the different colors within the light.
Students will use their spectroscopes to look at different lights in the classroom to see what different colors they produce.
Next, students compare the spectra of different light sources with their spectroscope for different light sources in our classroom. I use the spectroscope sheet for examples of light sources the students can use. (simple-spectroscope)
(Note differences in the colors and the spacing of the spectra. An incandescent bulb should produce a continuous spectrum where one color blends into another. A fluorescent bulb should create more distinct spectra, with less power in many wavelengths.)
In this video, you can see my busy classroom. Students move around the classroom, looking at various lights. Notice how the two boys in the beginning are conversing about the differences between different light sources.
After students have finished observing various light sources with their spectroscopes, I direct them to record their observations in their science notebook. Listen in to this video as students record their findings.
To wrap up this lesson and help explain the science behind why the spectroscopes work, I show this video. Students are very impressed with what they see, but this video helps make the science behind the spectroscope clearer. Light waves are still an abstract concept for fourth graders. I find using video tutorials and explanations help my students gain understanding.
Interactive Assistance: As I assist students with the activity, I ask what they are learning and discovering through the process. I encourage students to try their spectroscope on many different light sources in the classroom.