1. Energy Traveling in Waves
Pre-Lab Introduction to Wave Terminology
Integrated Science
Unit 1: Energy & the Solar System

2. Don’t forget to take your pre-lab paper with you to your lab class!
Instructions
Use the information included in this presentation to help you complete the pre-lab assignment for lab this week. To help you check your understanding, questions are included with each topic, and answers to all questions are posted at the end of this presentation.
Don’t forget to take your pre-lab paper with you to your lab class!

3. Definition
A wave is defined as a disturbance that carries energy from one place to another.
For example, a wave on a rope does not carry bits of rope from one end to the other, but instead carries energy from one end to the other, using the rope as the substance (or medium) that vibrates to carry the energy along its length.

4. Categories
All waves are categorized as either mechanical or non-mechanical. All waves are also classified as either transverse or compression.
A mechanical wave requires a substance (or medium) in order for it to transmit. A non-mechanical wave needs no substance (or medium).
Question #1
Are light waves from the Sun mechanical or non-mechanical? How can you be sure?

5. More Categories
Transverse and compressional waves are categorized based on the direction of the source vibration that causes the wave.
Compression waves (shown to the right) are created when the source moves parallel to the direction the wave travels.
Transverse waves (shown to the right) are created when the source moves perpendicularly to the direction the wave travels.

6. Question #2
A girl makes a wave pulse on a rope by vibrating the rope up and down, and the wave moves away from her. Is her wave mechanical or non-mechanical? Is it transverse or compression?

7. Transverse Wave Parts
Crests and troughs describe places on a transverse wave. Amplitude and wavelength are both measurements about a wave.

8. Transverse Wave Parts
Crests are the highest points on a wave above the rest position.
Troughs are the lowest points on a wave below the rest position.
Crests
Troughs

9. Transverse Wave Parts
Wavelength is the distance, measured along the wave’s direction, from one crest to the next crest (or from a trough to the next trough).
Amplitude is the distance from the rest position out to either a crest or to a trough.
Wavelength
Amplitude

10. Question #3
Find the amplitude and wavelength of the wave shown in the diagram below.
90cm
40cm

11. Frequency
Frequency is a measure of how quickly a wave vibrates. Specifically, it is the number of complete vibrations per second measured at a fixed location.

12. Answers to Questions
1. Light waves must be non-mechanical, since they are able to travel to Earth from the Sun through space. Space is empty, where there is no substance for the waves to travel through.
2. Her wave is mechanical since it travels through a medium. (The wave couldn’t exist without the rope.) It is also transverse, since the source vibrates up and down, which is perpendicular to the direction that the wave travels.
3. Amplitude=20cm (from rest position to crest)
Wavelength=60cm (2/3 of the pictured length)