Total Time: 30 - 45 minutes
Audience: Middle School Science Teachers
Education Level: Grades 5 - 9
Content Area: Waves, Energy
Educational Topic: Waves, energy, light
Objectives: Students will experiment with the idea that different colors of light are not the same, but vary in wavelength and energy.
Key Question: What is the difference between red light and blue light?
MS-PS4-1. Use mathematical representations to describe a simple model for waves that includes how the amplitude of a wave is related to the energy in a wave.
MS-PS4-2. Develop and use a model to describe how waves are reflected, absorbed, or transmitted through various materials.
MS-PS4.A: Wave Properties
SEPs: Scientific Knowledge is Based on Empirical Evidence ▪ Scientific knowledge is based upon logical and conceptual connections between evidence and explanations. (MS-PS4-1)
CCCs: Patterns ▪ Structure and Function
You’ll need one of each color of light per sheet of phosphorescent paper. One set of materials per student is ideal, but small group work is certainly possible.
Overview: Students start by discussing the questions, “What do you think makes red light different from blue light? Does one have more energy than the other? How could we find out?” Students will then engage in an experiment where they explore red and blue lights to answer the key question, “What makes red light different from blue light? And what does this have to do with Einstein’s Nobel Prize?”
Watch this video from Little Shop of Physics for an overview of the experimental setup and the science behind the phenomenon!
Albert Einstein received a Nobel prize for his explanation of the photoelectric effect. Einstein’s contribution was the realization that light had a particle nature as well as a wave nature. Light is made of individual particles or packets of energy called photons. Different colors of light have photons of different energies. Photons of red light have lower energy; photons of blue light have higher energy. Suppose you need to get a gallon of milk. You could get two half-gallon bottles, or you could get four-quart bottles. The total amount of milk is the same — but it comes in different-sized “chunks.” If you have blue light, it is like getting your light in half-gallon bottles; with red light, it is like getting your light in quart bottles.
When you charge up the phosphorescent paper included in this activity, the individual molecules within the paper can only absorb one photon at a time. If the absorbed photon has enough energy, the molecule will give back some light energy (along with some thermal energy). The amount of light energy given back is less than the amount of light energy absorbed, and so is a different color than the input light. The red photons don’t have enough energy to make the paper glow, but the photons of blue light do. At the far end of the spectrum, ultraviolet photons have a lot of energy — they are quite zesty. That’s why they can give you a sunburn! The same goes for the entire electromagnetic (EM) spectrum, even outside the range our eyes can see. The EM spectrum is a continuous gradient from low-energy radio waves (these are a type of light too!) to higher and higher energies of light, the highest of which we call gamma rays.
Students will experiment with the idea that different colors of light are not the same, but vary in wavelength and energy.*
*It is important to understand that student goals may be different and unique from the lesson goals. We recommend leaving room for students to set their own goals for each activity.
Watch this video from Little Shop of Physics for an overview of the experimental setup and the science behind the phenomenon!
You’ll need one of each color of light (red and blue) per sheet of phosphorescent paper. One set of materials per student is ideal, but small group work is certainly possible.
Tell students the day before the activity to bring any glow-in-the-dark clothes/objects/materials from home to use in our experiment!
Important Note: Listen in on each group’s discussion, and answer as few questions as possible. Even if a group is off a little, they will have a chance to work out these stuck points later during the discussion.
:
The different colors of light are not the same. We are going to explore and find out whether red light or blue light has more energy and what this has to do with Albert Einstein’s Nobel Prize.
Objective: Students will experiment with the idea that different colors of light are not the same but vary in wavelength and energy.
Students: After reading the introduction, what is your essential question or objective for this activity?
**Real-world situations/connections can be used as is, or changed to better fit a student’s own community and cultural context.
Created by Cherie Bornhorst, MEd, and Little Shop of Physics along with Nicole Schrode, MEd, and Claudia Fracchiolla, PhD, of APS Public Engagement
Reviewed by Summer Chrisman, MEd, Tamia Williams, MSt, Chris Irwin
Extensions by Jenna Tempkin
Formatted by Sierra Crandell, MEd, partially funded by Eucalyptus Foundation PhysicsQuest © 2023 by American Physical Society is licensed under CC BY-NC 4.0