Energy in Motion: Waves and Information · Term 2

Light and Reflection

An investigation into how light interacts with various objects through reflection, refraction, and absorption.

About This Topic

This topic investigates the behavior of light as it interacts with different surfaces and materials. Students explore the concepts of reflection (bouncing off), refraction (bending), and absorption (soaking in). The Ontario curriculum encourages a hands-on approach to light, as it is a primary way we gather information about the world. By using mirrors, lenses, and prisms, students see how light can be manipulated to solve problems or create art.

Students also learn about the visible spectrum and how white light is composed of many colors. This unit provides a great opportunity to discuss how different cultures, including Francophone and Indigenous communities, have used light and color in their traditions and technologies. This topic comes alive when students can physically model the patterns of light rays using flashlights and physical barriers.

Learning Objectives

• Explain how light rays reflect off smooth and rough surfaces.
• Analyze how lenses refract light to magnify or shrink images.
• Compare the effects of reflection, refraction, and absorption on light passing through different materials.
• Predict how changing the angle of incidence affects the angle of reflection.
• Identify the colors present in white light using a prism.

Before You Start

Properties of Light

Why: Students need a basic understanding that light travels in straight lines and is necessary for seeing.

Materials and Their Properties

Why: Understanding that different materials have different properties, such as being smooth or rough, transparent or opaque, is foundational for exploring light's interaction with them.

Key Vocabulary

reflection	The bouncing of light off a surface. For example, you see your reflection in a mirror because light bounces off it.
refraction	The bending of light as it passes from one material to another. This is why a straw looks bent in a glass of water.
absorption	The process where light energy is taken in by a material. Dark surfaces absorb more light than light surfaces.
angle of incidence	The angle at which a light ray strikes a surface. It is measured from the surface's perpendicular line.
angle of reflection	The angle at which a light ray bounces off a surface. It is equal to the angle of incidence.

Active Learning Ideas

Stations Rotation: Light Lab

Set up stations with mirrors (reflection), glasses of water with pencils (refraction), and black vs. white paper (absorption). Students must predict what will happen at each station before testing it and recording the results.

⏱ 60 min·Small Groups

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Inquiry Circle: The Periscope Challenge

Groups are given mirrors and cardboard tubes and must design a periscope that allows them to see over a 'wall' (a tall box). They must draw the path of the light rays to show how reflection makes this possible.

⏱ 50 min·Small Groups

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Gallery Walk: Shadow Puppetry

Students create shadow puppets to demonstrate how light travels in straight lines and is blocked by opaque objects. They present short scenes while the rest of the class identifies where the light is being absorbed or reflected.

⏱ 35 min·Small Groups

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Real-World Connections

Optical engineers use principles of reflection and refraction to design telescopes and microscopes, allowing us to see distant stars or tiny cells.

Architects use knowledge of light absorption and reflection when choosing materials for buildings to control heat gain and create specific lighting effects.

Photographers adjust lenses and lighting, understanding how refraction bends light, to capture clear and well-exposed images.

Watch Out for These Misconceptions

Common Misconception

We see because light comes out of our eyes.

What to Teach Instead

We see because light reflects off objects and enters our eyes. Using a 'dark box' experiment where students try to see an object with no light source helps correct this ancient misconception.

Common Misconception

Light only reflects off mirrors.

What to Teach Instead

Light reflects off almost everything, which is why we can see non-luminous objects. Peer discussion comparing a mirror to a piece of paper helps students understand the difference between regular and diffuse reflection.

Assessment Ideas

Quick Check

Provide students with a flashlight, a mirror, and a dark piece of paper. Ask them to demonstrate reflection by aiming the light at the mirror and observing where it bounces. Then, have them place the dark paper in the light path and describe what happens to the light.

Discussion Prompt

Pose the question: 'Imagine you are designing a room for reading. What surfaces and objects would you choose to make the room bright and easy to see in, and why?' Guide students to discuss reflection and absorption in their answers.

Exit Ticket

Give students a card with a diagram showing light moving from air into water. Ask them to draw the path of the light after it enters the water and label it 'refraction.' Then, ask them to explain in one sentence why the light bent.

Frequently Asked Questions

How can active learning help students understand light and reflection?

Light is often abstract because it moves so fast. Active learning, like building periscopes or using flashlights in a darkened room, slows the process down. When students have to physically align mirrors to hit a target with a beam of light, they are forced to internalize the 'angle in equals angle out' rule of reflection.

What is the difference between transparent, translucent, and opaque?

Transparent materials let all light through (clear glass), translucent let some through (wax paper), and opaque let no light through (wood).

Why does a straw look broken in a glass of water?

This is refraction. Light slows down when it moves from air into water, which causes the light rays to bend, making the straw appear to be in a different spot.

How do we see color?

An object appears a certain color because it reflects that specific color of light and absorbs all the others. A red apple reflects red light and absorbs the rest of the rainbow.