Lesson Plan - Get It!
How fast does light move? When you sit in the sun to "catch a few rays," you're probably not being literal!
Do you think light travels fast or slow?
Tell your teacher or parent. Light could easily beat the fastest car in a NASCAR race, and can travel from New York to London faster than any jet!
Light travels at a speed of 186,000 miles per second! It takes light less than eight and a half minutes to travel 93 million miles, from the sun to Earth. Now that's fast!
Light travels as a transverse wave. To learn exactly what a transverse wave is, watch the video Physics - Waves – Introduction. by expertmathstutor (below):
What is the difference between a transverse wave and a longitudinal wave?
- In a transverse wave, the vibrations are perpendicular to the direction the wave is traveling.
- In a longitudinal wave, the vibrations are parallel to the direction the wave is traveling.
Get a Slinky, if you have one. Hold one end of the Slinky while your teacher or parent holds the other end a few feet away from you. Hold your end still while your teacher or parent moves their end up and down. You have just created a transverse wave. Discuss what you observed about the movement of the Slinky with your teacher or parent.
There are four terms you need to know when studying a transverse wave: crest, trough, wavelength, and frequency. These terms were also discussed in the video.
A crest is the highest point on a wave, and a trough is the lowest point on a wave.
Wavelength describes the distance between two waves. A wavelength can be measured from any point on a wave, as long as it is measured to the same point on the next wave. Point to where the wavelength is labeled below.
When measuring wavelengths, use the metric units millimeters and centimeters unless another unit is specified. You have to know what a wavelength is in order to find the frequency. Frequency is the number of wavelengths (or cycles) in a wave during a fixed period of time, usually seconds.
Look at the picture below, illustrating one second. What is the frequency of the wave? Did you say two? That's correct! The light wave pictured has a frequency of two cycles per second because there are two full wavelengths pictured.
The frequency of a light wave is proportional to its energy. A high-frequency wave has high energy. A low-frequency wave has low energy. Do the waves pictured above have high or low energy? Share your answer with a teacher or parent and explain your reasoning.
Think you understand all the parts of a light wave? Move on to the next section to find out!