Do different light sources produce different light waves? In this activity, you will make a spectroscope, which is a device used for looking at the different colors that make up light.

Build a Spectroscope

Do different light sources produce different light waves?

Key Concepts

  • Diffraction

     

  • Interference

     


  • Introduction

    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.

  • Background

    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.

  • Preparation

    To make the spectroscope:

    • Cut a slit near the bottom of the tube, angled at about 45˚ toward the end of the tube. The slit should only cut about halfway through the thickness of the tube.
    • On the back side of the tube, directly across from the slit, cut a small peephole so you can see into the tube.
    • Next, trace the other end of the tube on the cardstock or cardboard.
    • Cut out the circle and cut a thin rectangular slit in the middle, about 1/8” wide.
    • Tape the circle to the top of your spectroscope.
    • Slide the CD with the shiny side up into the slit near the peephole, and secure with tape if necessary.

       

  • Procedure

    1. Make a prediction. How will light look when it bounces off the CD?
    2. Put your eye to the peephole and look at the CD inside the spectroscope. Try looking at different things: The sky, a lightbulb, a flashlight, etc. IMPORTANT: Do NOT look directly at the sun with your spectroscope, as this can permanently damage your eyes.
    3. Compare the differences between different light sources.
  • Observations and Results

    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.

  • Clean Up

    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.

  • More to Explore

    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.

  • Safety First & Adult Supervision

    • Follow the experiment’s instructions carefully.
    • A responsible adult should assist with each experiment.
    • While science experiments at home are exciting ways to learn about science hands-on, please note that some may require participants to take extra safety precautions and/or make a mess.
    • Adults should handle or assist with potentially harmful materials or sharp objects.
    • Adult should review each experiment and determine what the appropriate age is for the student’s participation in each activity before conducting any experiment.

Next Generation Science Standard (NGSS) Supported – Disciplinary Core

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.

Disciplinary Core Ideas in Engineering Design & Physical Science

Physical Science (PS)4: Waves and Their Application in Technologies for Information Transfer

Grades 3-5

  • 4-PS4-1. Waves of the same type can differ in amplitude (height of the wave) and wavelength (spacing between wave peaks).

Grades 6-8

  • MS-PS4-1. A simple wave has a repeating pattern with a specific wavelength, frequency, and amplitude.

Grades 9-12

  • HS-PS4-1. The wavelength and frequency of a wave are related to one another by the speed of travel of the wave, which depends on the type of wave and the medium through which it is passing.
  • HS-PS4-3. Waves can add or cancel one another as they cross, depending on their relative phase (i.e., relative position of peaks and troughs of the waves), but they emerge unaffected by each other.

Grades K-2

  • 1-PS4-2. Objects can be seen only when light is available to illuminate them. Some objects give off their own light.

Grades 3-5

  • 4-PS4-2. An object can be seen when light reflected from its surface enters the eye.

Grades 6-8

  • MS-PS4-2. When light shines on an object, it is reflected, absorbed, or transmitted through the object, depending on the object’s material and the frequency (color) of the light.
  • MS-PS4-2. The path that light travels can be traced as straight lines, except at surfaces between different transparent material (e.g., air and water, air and glass) where the light path bends.
  • MS-PS4-2. A wave model of light is useful for explaining brightness, color, and the frequency-dependent bending of light at a surface between media.

Grades 9-12

  • HS-PS4-3. Electromagnetic radiation (e.g., radio, microwave, light) can be modeled as a wave of changing electric and magnetic fields or as particles called photons. The wave model is useful for explaining many features of electromagnetic radiation, and the particle model explains other features.
  • HS-PS4-4. When light or longer wavelength electromagnetic radiation is absorbed in matter, it is generally converted into thermal energy (heat). Shorter wavelength electromagnetic radiation (ultraviolet, X-rays, gamma rays) can ionize atoms and cause damage to living cells.
  • HS-PS4-5.Photovoltaic materials emit electrons when they absorb light of a high-enough frequency.
  • (HS-ESS1-2). Atoms of each element emit and absorb characteristic frequencies of light. These characteristics allow identification of the presence of an element, even in microscopic quantities.