“Reflects, Absorbs, or Allows Light to Pass Through”
3rd Grade Science, Unit 2: “Light and Sound”
GLCEs:
P.EN.03.21 Demonstrate that light travels in a straight path and that shadows are made by placing an object in a path of light.
S.IP.03.11 Make purposeful observations concerning sound and light.
S.IA.03.12 Share ideas about sound and light through purposeful conversation in collaborative groups.
S.IA.03.13 Communicate and present findings of observations and investigations about sound and light using evidence.
Background:
Light travels in straight paths, which move out from the source until they hit or interact with something. When light strikes an object, it is reflected, passes through or absorbed.
A shadow is formed when an opaque object blocks the path of light (opaque objects do not allow light to pass through).
A common misconception is that shadows are independent of the object that causes them and that a light source and its effects are not separate.
Vocabulary:
light
path of light
light source
light absorption
light reflection
opaque (useful, but notState Assessable)
Materials:
- 1 shoe box and lid with one inch whole in endper group
It would be helpful for the teacher to collect and cut the shoe boxes ahead of time.
- 1 flashlight for each group
- Materials that either reflects, absorbs, or allows light to pass through.
***The instructor needs to provide multiple copies of the same objects such as lined paper, construction paper, a book, a mirror, a plastic bag, clip board, water bottle, transparency, etc.
Procedure:
- Get flashlight and a cardboard box that can hold the flashlight inside it.
- Tape the flashlight in the box so that it is pointing toward the hole in the end of the box.
- Switch on theflashlight and close the box with its lid.
- Take the box to a dark place, where there is little or no light. The light escaping from the box should be coming from the hole.
- Begin covering the hole with the objects that your teacher has given you.
- Record what happens with each object.
Put an X in each rectangle that is true about your object
object / reflects light / light passes through / absorbs light
Many objects will fit into more than one column. For example, colored objects will reflect the color they appear and absorb other colors in the spectrum. Black absorbs all colors, white reflects all Also a mirror), the rest are somewhere in the middle. Transparencies and the like will let almost all light pass through.
Turn off the flashlight. Use the colored piece of construction paper. While it is in the dark room in the box, does the paper look bright? Is it easy to tell the color of the paper? Why?
There should not be enough light in a darkened room with the light off for the children to see the colored paper. There is no source of light to reflect the light into the child’s eyes.
Explanation
We see objects because they either emit light or reflect light.
Light travels in straight lines from a source such as the sun or a light bulb. When light strikes an object, it is reflected, absorbed, or it passes through the object.
When light is reflected or bounces off an object, the light waves travel in straight lines until they reach the eye. The light enters the eye through the pupil and we see the object.
A common misconception at this grade level is that the eye gathers light.
A common misconception is that we can see in a completely darkened room.
Group Activity:
The instructor may want to hold up a few different sheets of construction paper in a well darkened room. If the room is dark enough, the children should not be able to identify the color of the paper. If they ca, there is too much light leaking into the room.
Teacher should provide an irregularly shaped object for the next section.
Extension:
Remove the flashlight form the box. Use an object given to you to create shadows on the wall.
How do you make the shadow of your object bigger?
Move object closer to light source
Are you able to change the shape of your object? How?
Twist or move the object such as a plastic coffee lid
Is there anything else you can do to change how the shadow of your object looks? How did you do it?