Lesson 1: Introduction to Concepts in Light

Light Lesson 1: Introduction to Concepts in Light

Time frame: 60 minutes

Please write the vocabulary words on the board before the lesson

Vocabulary Light- The natural agent that stimulates sight and makes things visible Shadow- A dark area or shape produced by a body coming between rays of light and a surface Angle- The space (usually measured in degrees) between two intersecting lines or surfaces at or close to the point where they meet.

Objectives Students will be able to 1. Come up with a definition for what light is 2. Create an experiment showing that light travels in a straight line 3. Understand how light’s path causes shadow direction and size

Introduction

Review the electromagnetic spectrum poster. Explain that light can travel as waves of different frequencies and that visible light only makes up a small fraction of the light waves around us. Light is a form of energy - it can cause objects to do work. For example, light energy can be transformed in plants to help them grow.

Ask students the following questions and write the answers on the board: 1.What is light? 2.Where is light? 3.What does light do? 4.Where does light come from? 5.What doesn’t have light? 6.How do you know?

Explain to the students that they already know so much about light. Light is all around us. It helps us see what’s in front of us. It enables us to see in color. It changes throughout the day etc. Explain that over the next few lessons they will discover through experiments some specific properties of light. Once they identify these characteristics, they will be able to find evidence everywhere they look. Focus Activity #1: How does light travel?

Ask students to create and conduct an experiment to discover whether light moves in a straight line or in a wave or as a cone or as a curve, etc.?

Materials Needed: ● three small index cards ● modeling clay ● flashlight ● several books ● hole puncher or sharp pencil ● plastic coffee stirrer or thin straw

Procedure: 1. Place the three cards together and punch a hole in the middle of each card at exactly the same spot using the pencil point or the hole punch. 2. Use three small balls of modeling clay to make the three cards stand up as shown. 3. Turn on the flashlight and place it in front of one of the cards. The bulb should be even with the hole in the card. If it isn’t use one or more books to raise the flashlight. 4. Once it is in place, you can secure it with modeling clay if needed. (You can also just hold the flashlight in place) 5. Now place the second card about 6 inches in front of the first card so that you can see the light through both holes. Do the same thing with the third card. 6. When you can see the light through all three holes, run the stirrer or straw through the holes. 7. Put a sheet of paper a few inches behind the third index card. You should see a circle of light on it.

What Happened: When the cards were lined up so that you could see the light, the holes were in a straight line, and the stirrer or broom straw fit easily through all three holes. When light moves away from an object, it moves in a straight line unless something acts on it to bend it.

Discuss with students what they discovered. How does light travel? How do they know? Can they think of any other experiments that can be done to prove it?

Activity #2: Shadows What makes a shadow? What determines how big a shadow is? Why do shadows change size during the day?

Put an object on the table. Move the flashlight around the object in a semi-circle as if it was the sun.

Fill out worksheet: Light and Shadows

Group questions after exercise: 1. What did you find was the relationship between your observational drawings (“draw the shadow”) and your directional light drawings (“draw the path of the light with a ruler”)? Did the direction of your shadow shift? Why?

2. Does the shadow get bigger or smaller when the flashlight is closer to the table? Why do you think this happens? (If they do not know, explain again how light moves in a straight line. Therefore at different angles, the ball blocks the light in various ways, which changes the size and direction of the shadow)

3. During the day, when do they think their shadows will be the biggest? When will their shadows be the smallest? Challenge your students to go home and measure their shadows at different times of the day.