In the Classroom

This activity is best designed for students between the fourth grade and high school-level  science class taught by an instructor that has some background in physics. This activity can also be done with PK to third grade students in a controlled environment. This activity allows students to explore and connect the relationship with wavelength, energy, and frequency with the basic principles behind the emission spectrum. The application involved can be seen using diffraction instruments created during this activity. PK – grade 3 students Start off by explaining how visible light is a spectrum that ranges from red to violet and how they differ in energy. To provide a visual aid for the students connect the colors on the spectrum to different flights of stairs (ie red –> low energy, short flight of stairs to jump down; violet –> higher energy, longer flight of stairs to jump down). Grade 4 – 6 students Students within this age should be able to connect wave properties with specific wavelengths, frequencies, and amplitudes with the concept of ROY G BIV. The color of light that is exhibited carries a set of properties relating to wavelength and frequency. Once again referring to the visible light spectrum, red will produce a lower frequency and shorter wavelength while, on the opposite end of the spectrum,  violet produces a shorter wavelength but higher frequency. Middle school students Diffraction gratings have tiny slits of grading which are used to separate light into colors we can see. In the visible wavelengths of the electromagnetic spectrum, the longest wavelength is diffracted the most, while the shortest wavelength is diffracted the least. Each color diffracts at a different amount meaning each color bends at a different angle. This leads to a separation of light which is seen with the help of the diffraction gratings. Science Discipline(s) Chemistry Physics Topics Emission spectrum, the relationship between: wavelength, energy, and frequency, diffraction and diffraction gratings Activity Title Colorful Gases Materials Scissors DVD or CD discs Box Cutter/ Razor Blade Tape Procedure DVD Diffraction Grating
  • Start by splitting a DVD disc using a razor or box cutter on the edge of the disc
  • Once you have your two split DVD discs, begin to take off the reflective layer of the disc using tape
    • Place the tape on the disc and peel off in the opposite direction it was applied
  • The transparent disc acts as the diffraction grating, cut disc into desired wedges using scissors then hold up wedge into light
CD Diffraction Grating
  • Begin by scratching off a section of the disc, preferably the label
  • Once the reflective portion of the CD is visible place tape over the scratched section of the disc and peel off in the opposite direction it was applied
  • The transparent part of the CD will act as the diffraction grating, cut disc into desired wedges using scissors then hold up wedge into light
  1. How many colors do you see when you put the diffraction grating up against different light?
  2. Which light seems to have the highest energy? Which has the lowest? Why?
  3. Based on the colors you see what properties do you think the light has?
  4. Why do some colors show up under the diffraction grating but not others?
Explanation Within an atom you have: electrons, protons and neutrons. When electrons jump from different orbitals in an atom they give off energy depending on the difference between the orbitals. Elements have different levels of energy thus exhibit different types of light. Those with a lower energy level give off a color within a red family while the elements with a higher energy exhibit a violet color. The light emitted carries it’s own set of properties regarding wave frequency and wavelength. Red exhibits a low frequency and longer wavelength while violet exhibits a shorter wavelength and higher frequency. Diffraction gratings have tiny slits that separate light into colors found within the visible light spectrum.  Depending on the properties of light, ie wavelength, frequency, energy, specific colors from the light spectrum will appear under the grating.  Next Generation Science Standards