Unit Plan 31 (Grade 8 Science): Light & the Electromagnetic Spectrum

Focus: Describe how electromagnetic (EM) waves (including visible light) carry energy and information, using amplitude and wavelength to represent wave patterns, and develop models showing how EM waves transfer energy but not matter as they interact with materials (absorbed, transmitted, reflected).

Grade Level: 8

Subject Area: Science (Physical Science • Waves & Information)

Total Unit Duration: 5 sessions (one week), 50–60 minutes per session

I. Introduction

In this unit, students extend their wave understanding to light and the electromagnetic (EM) spectrum. They learn that visible light is one small part of a broad spectrum of EM waves (radio, microwaves, infrared, visible, ultraviolet, X-rays, gamma rays) that all travel at the speed of light in a vacuum and can move through space without a medium. Students use diagrams and graphs to describe EM waves in terms of amplitude and wavelength, and they explore how wave patterns can carry information (e.g., radio, Wi-Fi, fiber optics). Through hands-on activities and simple models, they investigate how EM waves interact with materials—being absorbed, transmitted, or reflected—and develop models to show that EM waves transfer energy but not matter to objects they strike.

Essential Questions

• What are electromagnetic waves, and how is visible light related to other parts of the EM spectrum?
• How do amplitude and wavelength describe EM waves, and what do these properties tell us about energy and wave patterns?
• How can wave patterns (changes in amplitude, wavelength, or timing) be used to carry and encode information?
• How do EM waves interact with materials—being absorbed, transmitted, or reflected—and what happens to the energy when they do?
• How can we use models to show that EM waves transfer energy but not matter as they move from source to receiver?

II. Objectives and Standards

Learning Objectives — Students will be able to:

1. Describe the electromagnetic spectrum, identifying major regions (radio, microwave, infrared, visible, ultraviolet, X-ray, gamma) and comparing their wavelengths qualitatively.
2. Use mathematical representations (tables of wavelength, simple graphs, labeled diagrams) to describe EM waves in terms of amplitude and wavelength and to interpret wave patterns that carry information (e.g., on/off pulses or changing amplitudes).
3. Develop and use models (ray diagrams, wavefront diagrams, energy-flow arrows) to show how EM waves transfer energy but not matter from a source to a receiver.
4. Investigate and model how EM waves interact with materials through absorption, transmission, and reflection, and explain how these interactions relate to energy transfer (e.g., heating, visibility, color).
5. Construct a written or visual explanation that connects EM wave properties, interactions, and models to the standards MS-PS4-1 and MS-PS4-2.

Standards Alignment — 8th Grade (NGSS-based custom)

• MS-PS4-1 — Use mathematical representations to describe waves in terms of amplitude and wavelength and to show how wave patterns provide information about the source and/or medium.
• MS-PS4-2 — Develop and use a model to describe that waves transfer energy but not matter.

Success Criteria — Student Language

• I can place visible light in the electromagnetic spectrum and compare its wavelength to other EM waves.
• I can use numbers, labels, and graphs to describe EM waves’ amplitude and wavelength, and I can read simple patterns that represent information.
• I can create a model showing EM waves traveling from a source to a receiver, with energy moving but no matter traveling between them.
• I can explain how EM waves are absorbed, transmitted, or reflected by materials and what happens to the energy in each case.
• I can write or present a clear explanation that shows how EM waves carry energy and information while not carrying matter.