Have you ever double bounced someone on a trampoline? Or pumped a swing to make it go higher? These are both examples of constructive interference, or when a wave is amplified by adding energy to it. In this activity, you will make a spectroscope, which is a device used for looking at the different colors that make up light. Spectroscopes use slits and lenses to create interference patterns of light, so we can look more closely at what colors a light is made of.
The modern spectroscope was invented by a German glassmaker named Joseph von Fraunhofer in 1814. He was a pioneer in many different techniques of glassmaking, and was very interested in how light and colors could be manipulated with glass. He did many experiments with his spectroscope, like looking at the sun’s spectrum, and comparing it to other stars in the sky, founding the field of research known as stellar spectroscopy.
To make the spectroscope:
You should see a rainbow appear on the CD when you look at the sky. This happens because the slit at the top, and the CD diffract the light that is coming into the spectroscope. Diffraction happens when waves pass through a slit, and bend and spread out. When light waves encounter lots of little slits or ridges, like on the surface of a CD, they interfere with each other. This interference can make some colors brighter, and some go away. Some of the waves build on each other, like double bouncing on a trampoline, and some of the waves cancel each other out, which takes certain colors away. The CD is showing interference patterns that can change, based on the different kinds of light that shine into the spectroscope.
You should see a rainbow appear on the CD when you look at the sky. This happens because the slit at the top, and the CD diffract the light that is coming into the spectroscope. Diffraction happens when waves pass through a slit, and bend and spread out. When light waves encounter lots of little slits or ridges, like on the surface of a CD, they interfere with each other. This interference can make some colors brighter, and some go away. Some of the waves build on each other, like double bouncing on a trampoline, and some of the waves cancel each other out, which takes certain colors away. The CD is showing interference patterns that can change, based on the different kinds of light that shine into the spectroscope.
Diffraction and interference are really useful ideas in studying stars. We use interference patterns of light from stars to help determine what stars are made of. Try looking up some images of different lights’ spectra, and comparing them to images of stars’ spectra.
This experiment was selected for Science at Home because it teaches NGSS Disciplinary Core Ideas, which have broad importance within or across multiple science or engineering disciplines.
Learn more about how this experiment is based in NGSS Disciplinary Core Ideas.
Physical Science (PS)4: Waves and Their Application in Technologies for Information Transfer