W.3+-+Nature+of+Science+Reading

W.3: Sound and Light © 2019 PEER Physics W.3 N ATURE OF S CIENCE R EADING Instructions: The purpose of this Nature of Science reading is to contextualize and formalize the Crosscutting Concepts and Science Practices from this activity. Physics principles (Disciplinary Core Ideas) were formalized in the Scientist’s Ideas reading. These three pieces– Crosscutting Concepts (CCCs), Science Practices (SEPs), and Disciplinary Core Ideas (DCIs) - are often referred to as “the Three Dimensions” of science learning. As you read, consider the ways you engaged in and with the three dimensions throughout this activity. W.3f CCCs & SEPs – Developing a model for a different phenomenon with wave like properties: Since sound and light phenomena involve similar patterns and characteristics, scientists can apply wave models and wave properties to explain them and relate them to our senses. However, wave models for sound and light also include important differences. Scientists can apply similar models to different phenomena that share important characteristics. In this activity, you revised your wave model for sound, and also created an initial wave model for light. It might have been surprising to you that the phenomena of sound and light can both be represented and explained through different kinds of wave models. In science, it is common for a similar kind of scientific model to be applied to different phenomena, as long as those phenomena have similar properties. This is the case for sound and light. Even though we perceive them very differently, these phenomena share some important characteristics. For instance, both sound and light involve a form of energy being emitted from a source, which travels from place to place. Both sound and light involve different kinds of repeating disturbances that are able to travel from place to place, and so both phenomena can be described in terms of amplitude, frequency, and wavelength. In other words, both sound and light are examples of what scientists would call wave phenomena, since they can both be explained using similar scientific terms and wave models. Applying similar models to different phenomena helps scientists highlight differences between them. Even though sound and light phenomena share some characteristics, scientists must keep in mind the differences that exist between them and highlight those differences in their models for each phenomenon. In this activity, you did this by contrasting whether each phenomenon requires a particle medium to exist. In the case of sound, evidence from prior activities supports the claim that sound does need a particle medium to exist. Your model of sound describes this phenomenon as being produced by collisions between particles, so without some kind of medium there would be nothing to disturb! On the other hand, your evidence about light supports a different claim, one that requires you to think about light in a different way than sound, even though these phenomena might be similar in other ways. From your observations of the radiometer, as well as your ideas about sunlight and how it travels through space, you could infer that light energy does not require a particle medium to travel.

W.3: Sound and Light © 2019 PEER Physics This is a key difference between sound and light waves, and one that requires us to change the way we think about light. Since light does not need a particle medium, your wave model of light represents this phenomenon not as a longitudinal wave (which is the case for sound), but rather as a transverse wave. Both longitudinal and transverse waves can be represented using wave diagrams, but wave diagrams for sound and light represent amplitude (in other words, the intensity of disturbances) differently. While sound and light can both be explained with wave models, each model explains the relationships between wave properties and our senses in a different way. To be able to use a wave model for light, it is important to include ideas about what the disturbances in a light wave might be, as well as how wave properties like frequency and amplitude influence our perception of light. The simulated model you explored in this activity provided you with information to begin developing these ideas. For instance, while sound is produced by repeating disturbances in a particle medium, the simulated model represents light as being produced by a repeating interaction between electricity and magnetism. These phenomena do not need a medium to exist, which helps us explain why light can travel even where there are no particles to disturb. The simulated model also gave you visual representations of how changing a light wave’s frequency and amplitude affects our perception of the light’s color and brightness. In short, both sound and light waves can be described using ideas about wavelength, frequency, and amplitude, but models of sound and light interpret these scientific terms differently and relate them in different ways to our senses. Wave concept Sound perception Sound model reasoning Light perception Light model reasoning Frequency Pitch How many times particles are cycling back and forth in a sound wave Color How many times the electromagnetic field is cycling in a light wave Amplitude Volume How dense and compressed with particles the disturbances are in the sound wave Brightness How intense the electromagnetic field disturbances are in the light wave Wavelength Pitch How far apart the disturbances in the sound wave are Color How far apart the disturbances in the light wave are

W.3: Sound and Light © 2019 PEER Physics 6. Which experiment from this activity provided you with the best evidence that light is a wave like phenomenon? Describe the evidence you collected and why you think it is important. 7. What are some ways in which the simulated model allowed you to explore light at a different scale? 8. What evidence from this activity supports the claim that light does not need a medium in order to travel? 9. Why do you think it can be important for scientists to apply similar models for different phenomena? 10. Describe how wave models for light and sound are similar in the way they describe the movement of sound and light. 11. In what ways did the simulated model give you evidence to interpret how frequency and amplitude affect light waves?