Grades: 1 to 5
Duration: 1/2 Hour – 1 Hour
NGSS Connections PS4.B: Electromagnetic Radiation
- Plan and conduct investigations to determine the effect of placing objects made with different materials in the path of a beam of light.
- Some materials allow light to pass through them, others allow only some light through and others block all the light and create a dark shadow on any surface beyond them, where the light cannot reach. (1-PS4-3)
- Cause and effect relationships are routinely identified (4-PS4-2)
Supplies: 3 Light BLOX in Red/Green/Blue, A pencil or pen, a blank wall or screen
Background for teachers: Exploring Shadows
Very young children think of shadows as actual objects. But by grade school, most kids will understand that a shadow is a phenomenon caused by blocking light. Most, however will not be able to articulate the relationship between the location of the light and the size and shape of the shadow. This exploration will give them a chance to develop an intuitive sense of light and shadow. Set up each group of students with one set of materials and the worksheet. When worksheets are done, hold a classroom conversation that incorporates students’ points and covers these main discussion points
A shadow “grows” in the same direction as the light travels. If you point the light from left to right, the shadow appears to the right of the object. If you point the light from right to left, the shadow appears tot he left of the object. A shadow gets bigger as the light moves further from the object. A shadow disappears when light strikes an object from directly above it.
Set up for Exploring Shadows
First, we’re going to create our own patch of white light to see what it’s made of!
Make White Light for Exploring Shadows
Take the caps off and switch on the red, green and blue Light BLOX. Try to create a patch of white light on the blank screen or wall, using only these three lights. You can combine them in any way you want. What did you need to do to create white light? What is white light made of?
Create and Explore Shadows
Now, let’s create a shadow and see if we can figure out how it works.
Place the long, thin object about 3 inches in front of the white screen. You’ll want the object to stand up straight.
Switch on the white Light Blox, and shine it directly onto the object, towards the screen. Hold the light about 2 inches from the object.
Try to make the shadow bigger, then smaller, by moving the LIGHT. What do you have to do to make this happen?
Now try to change the size of the shadow by moving the OBJECT. What do you have to do?
Make the shadow move to the left of the screen. What did you do? How can you make the shadow move to the right?