Objective Since light rays are intangible, many students find it difficult to comprehend crests and wavelengths.
This lesson will give students the ability to bring concreteness to these abstract concepts. The students will be able to see and identify crests and wavelengths.
Material Needed Closed door, with a doorknob, 3-meter length of rope.
Procedure
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1. Tie one end of the 3-meter rope to the doorknob of a closed door.
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2. Hold the rope loosely at the height of your waist.
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3. Flip the rope up and down until the rope makes waves.
Observations and Analysis
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1. The hills formed by the rope are called crests.
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2. The faster the rope is flipped, the more waves are formed. These waves are also closer together.
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3. The distance from crest to crest is called wavelength.
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4. The number of crests that pass a given point in a second is called frequency.
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5. One theory of light is that light travels in the form of waves at a speed of 300,000 km/second in a vacuum.
Vocabulary:
1. Intangible
2. Crest
3. Wavelength
4. Frequency
5. Meter
Vocabulary Study
Hi, boys and girls! My name is Mr. Meter. I am used to measure the length of objects. Have you ever seen a yardstick? Well, I’m just about that long. I am most useful if you need to measure something that is rather long, like the door in your classroom or your teacher’s desk. If you want to measure something smaller, then it would be better for you to use one of my children. Here, I’ll introduce you to them.
This is my oldest child, Deci. Deci is bigger than my other two children. Deci means ten. I named her Deci because I’m ten times larger than she is. It would be best to use Deci if you wanted to measure the length of a book, or the height of a medium sized stuffed animal.
My middle child is Centi. Centi means one hundred. I named him Centi because I’m one hundred times bigger than him. I’m ten times bigger than Deci, and Deci is ten times bigger than Centi. If you wanted to measure the length of a pencil, Centi is the one you would probably use.
Last but not least is Milli. Milli is so very tiny. Milli is a prefix that means one thousand. I named her Milli because I’m one thousand times larger than she is. Milli enables people to measure the very tiny things in life, like the eraser on a pencil or the button on a baby’s coat.
Now that you’ve met us all, decide which of us you would use to measure
1. A dresser
2. A baby’s shoe
3. A wedding ring
4. A pencil eraser
5. A drinking glass
6. A full size bed
