Kayla Rice - Light Tricks

Principles:

· White light is made up of all the colors of the rainbow.

· Making accurate observations is an important skill.

Standards: California State Science Standard:

7.6.e. Students know that white light is a mixture of many wavelengths (colors) and that retinal cells react differently to different wavelengths.

*Note: We do not get into the retinal cell part of this standard. It may be mentioned, but is not something that is usually tested.

Materials:

Lamp, without shade

Incandescent or Compact Florescent light bulb

Magic Light Card – Three different colored lenses (I used red, green and diffraction lenses), cut apart (originally from three different glasses) and taped together(one of each color per card). Glasses may be purchased at http://www.rainbowsymphony.com. Look for “Rainbow Glasses” for the diffraction lens.

Procedure:

· Students are beginning to reflect on what they know about light and how they know it – A concept map is a good way to do this (AKA the donut map) with light in the center, what they know about light around it, and where they know this from in the context box.

· The teacher leads the students to look through the “magic light card” at different objects in the room and record observations. The students are first directed to look at a white board with the red lens and write observation, the green lens and write observations, and the clear lens. (Pictured below is a white door viewed with the naked eye, a red lens and a green lens.)

· Students add at least five more items in the room and describe how they look with each lens. (This is best organized in a three-column data table.)

· With as little external light as possible and the room lights off, the students look at a white light bulb through the clear (diffraction) lens. They diagram it in COLOR!

· Discuss where the colors came from, what does that tell us about white light, and of what is white light made.

Prior Knowledge:

· Students need to know how to make accurate observations; even though, this will help them practice.

· Students need to know that light is made up of waves that travel through the air.

Explanation:

The first point of this experiment is to get the students interested in light. Light is kind of an odd topic to jump right into at the beginning of the semester, but it’s also crucial for all of the other units.

The big idea that will be gained by this experiment is that white light is made up of all of the colors of the rainbow. The diffraction lens has ridges on its surface to diffract the light and split the white into the rainbow; be certain to tell the students this. Make note, that using a different kinds of light bulb has a different effect. If you use an incandescent bulb, the students will see a “block” of the rainbow; whereas, if you use a compact florescent bulb, the students will see three or four bulbs at each radius of the rainbow. With the CFL, the students will still see all of the colors of the rainbow, but the colors will be throughout the overlapping bulbs. One other interesting thing that I noticed about the bulbs: the bulbs are prominent at red, green and blue light; the places where they overlap are where you see the other colors.

This lab is also a good lead into absorption, reflection and transmission of light through matter.

Question and Answer:

1. When you look at the light bulb through the diffraction lens, what do you see? Draw this.

(See photo above) *This will get the students thinking about the order of the colors and help them study the light (instead of just looking at it once). It will help them commit what they see to memory.

2. From where did the colors of the rainbow come?

The colors of the rainbow come from the white light. The white light hits the diffraction ridges on the lens and diverts the different colors by their wavelengths.

3. So, what is white light made of?

White light is made of all the colors of the rainbow. Each color has a different wavelength, and when added together, they make white light.

Applications to Real Life:

We use light in almost every part of our lives. We get light from the sun, from light bulbs, even from our computer screens. Light from the sun is used in photosynthesis and is a key factor in the survival of life. Sunlight brings warmth to the earth as well. The light that our bodies, animals and the earth absorb in the form of heat keeps us warm and stabilizes our ecosystems. When we see colors we are really seeing the reflected light off of an object (in the coming lessons). Without light, we would see nothing!

References:

http://www.rainbowsymphony.com (for the lenses)

C. Waishwile. Personal interview and observation of experiment. February 17, 2011/