In this unit students investigate the characteristics of waves. Throughout the unit students contrast sound and light as particular examples of mechanical and electromagnetic waves. They examine transverse and longitudinal (compressional) waves on a Slinky™ or with online simulations. These simple but engaging tools allow students to experience first hand both types of waves and make basic observations and measurements of frequency, wavelength, amplitude, and wave speed, and their relationship. Additionally, the observation that waves transfer energy with no net transfer of mass is an important concept to allow for the comparison with how a moving object transfers energy. Net the relationship between the amount of energy transferred and the wave’s characteristic properties is addressed. Students then explore sound waves produced by vibrating strings and columns of air with special attention paid to identifying the source of vibration in various musical instruments along with the propagation of sound, so that everyone in a room hears the same notes simultaneously. They represent the reflection and refraction of light rays from mirrors and through transparent materials, such as lenses, using ray diagrams to show the behavior of light and the location and size of images produced. Students then compare the sources and nature of both sound and light waves emphasizing their similarities and differences. Finally they explore the identifying characteristics of surface waves and how they function to cause tsunamis and damage during earthquakes.
STANDARD P4: FORMS OF ENERGY AND ENERGY TRANSFORMATIONS Energy is a useful conceptual system for explaining how the universe works and accounting for changes in matter. Energy is not a “thing.” Students develop several energy-related ideas: First, they keep track of energy during transfers and transformations, and account for changes using energy conservation. Second, they identify places where energy is apparently lost during a transformation process, but is actually spread around to the environment as thermal energy and therefore not easily recoverable. Third, they identify the means of energy transfers: collisions between particles, or waves.
P4.1 Energy Transfer
P4.1B Explain instances of energy transfer by waves and objects in everyday activities (e.g., why the ground gets warm during the day, how you hear a distant sound, why it hurts when you are hit by a baseball).
P4.4 Wave Characteristics
P4.4A Describe specific mechanical waves (e.g., on a demonstration spring, on the ocean) in terms of wavelength, amplitude, frequency, and speed.
P4.4B Identify everyday examples of transverse and compression (longitudinal) waves.
P4.4C Compare and contrast transverse and compression (longitudinal) waves in terms of wavelength, amplitude, and frequency.
P4.4x Wave Characteristics — Calculations
P4.4d Demonstrate that frequency and wavelength of a wave are inversely proportional in a given medium.
P4.5 Mechanical Wave Propagation
P4.5A Identify everyday examples of energy transfer by waves and their sources.
P4.5B Explain why an object (e.g., fishing bobber) does not move forward as a wave passes under it.
P4.5C Provide evidence to support the claim that sound is energy transferred by a wave, not energy transferred by particles.
P4.5D Explain how waves propagate from vibrating sources and why the intensity decreases with the square of the distance from a point source.
P4.5E Explain why everyone in a classroom can hear one person speaking, but why an amplifi cation system is often used in the rear of a large concert auditorium.
P4.8 Wave Behavior — Reflection and Refraction
P4.8A Draw ray diagrams to indicate how light reflects off objects or refracts into transparent media.
P4.8B Predict the path of reflected light from flat, curved, or rough surfaces (e.g., flat and curved mirrors, painted walls, paper).
P4.9A Identify the principle involved when you see a transparent object (e.g., straw, piece of glass) in a clear liquid.
P4.9B Explain how various materials refl ect, absorb, or transmit light in different ways.
P4.9C Explain why the image of the Sun appears reddish at sunrise and sunset.
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- What are the defining characteristics of waves?
- How is energy transfer by waves different from other forms of energy transfer?
- How are sound and water waves different from and similar to light waves?
- How are sound waves produced?
- How is light reflected from plane and curved mirrors?
- How is light refracted by transparent materials and lenses?
compression (longitudinal) waves