1. The Nature of Waves
Unit 12
Section 1

2. I. Waves
A wave is any disturbance that transmits (carries) energy through matter or empty space.
Waves that travel through empty space are called electromagnetic waves.
Waves that travel through matter (solids, liquids or gases) are called mechanical waves.
Can you think of some examples of types of waves?

3. II. Medium
A medium (media) is a substance through which a mechanical wave can travel.
i. It is the physical environment in which something occurs.
A medium can be a solid, liquid, or gas.
Some examples of media are water, air, and the ground because waves can travel through them.
Waves that require a medium to travel through are
called mechanical waves.

4. III. Electromagnetic Waves
Electromagnetic waves are waves that do not need a medium to be able to transfer energy.
i. Examples: visible light, microwaves, T.V., radio signals or X rays that your doctor or dentist takes.

5. IV. Transverse Waves
Transverse waves are waves in which the particles of the medium (a solid, liquid or gas), move perpendicular to the direction the wave is moving.
(remember the rope activity in class)
b. The highest point of a transverse wave is called the crest.
c. The lowest point of a transverse wave is called a trough.
i. All electromagnetic waves are transverse waves.
ii. Another example is a rope moving up and down.

6. Example of a Transverse Wave

7. V. Longitudinal (Compressional) Waves
A longitudinal wave is also known as a compressional wave.
It is a wave in which the particles of the medium vibrate parallel to the direction of the wave motion.
i. The wave and the medium move in
the same direction.
ii. Example-slinky
iii. Example-sound waves

8. c. There are two parts of a longitudinal/compressional wave:
2. rarefaction
d. When the waves are pressed together, it is called compression.
e. When the waves are spread apart, it is called rarefaction.

9. Example of a Longitudinal Wave
Rarefaction
Waves far apart
Compression
Waves close together

10. Label the longitudinal wave below:

11. Quickie Quiz
In a _________________, the particles vibrate parallel to the direction that the wave travels.
surface wave
longitudinal wave
transverse wave
wave

12. Quickie Quiz
Mechanical waves require a ___________ through which to travel.
surface wave
biome
medium
transverse wave

13. Quickie Quiz What is not an example of a medium? a. air b. water
c. energy
d. soil

14. Quickie Quiz
In a ________________ , the particles vibrate perpendicularly to the direction that the wave travels.
surface wave
longitudinal wave
transverse wave
medium

15. Quickie Quiz
Waves transfer:
matter
energy
particles
water

16. Quickie Quiz
Label the parts of the wave below.