1. WAVES

2. A wave is a disturbance that transmits energy through matter or space.
What is a wave?
A wave is a disturbance that transmits energy through matter or space.

3. What is a wave?
There are 2 types of waves:
Mechanical
Electromagnetic

4. A mechanical wave must have a medium to be able to travel.
W a v e s
A mechanical wave must have a medium to be able to travel.

5. Electromagnetic Waves
Electromagnetic waves consist of alternating electric and magnetic fields in space and do not require a medium to travel.

6. Most waves travel through a medium
How do waves travel?
Most waves travel through a medium
A medium is the matter or “stuff” through which a wave travels
For example: Water, air, the ground, rock, etc.

7. How do waves travel?
Electromagnetic waves DO NOT require a medium, and actually travel best when in a vacuum.

8. How do waves travel?
Light waves consist of changing electric and magnetic fields in space which are called electromagnetic waves.

9. EXAMPLES OF ELECTROMAGNETIC WAVES
Radio Waves
Television Waves
Visible Light
X-rays
UV Rays

10. What do waves do?
Waves transfer energy

11. Does a wave travel on forever? Energy may spread out as a wave travels
What happens to a wave?
Does a wave travel on forever? NO
Energy may spread out as a wave travels

12. Waves are related to vibrations Waves are caused by vibrating objects.
Waves and vibrations
Waves are related to vibrations
Waves are caused by vibrating objects.

13. Particles in a medium can either vibrate
Transverse and
Longitudinal Waves
Particles in a medium can either vibrate
perpendicularly
parallel
to the direction of wave motion

14. EXAMPLES: Stadium wave, light wave
Transverse and
Longitudinal Waves
Transverse Waves
The particles of the medium vibrate perpendicularly to the direction the wave travels.
EXAMPLES: Stadium wave, light wave

15. Transverse and
Longitudinal Waves
Longitudinal Waves
The particles of the medium vibrate parallel to the direction the wave travels.
EXAMPLES: Sound Waves

16. Transverse and
Longitudinal Waves
In a surface wave, particles move in a circle. (perpendicularly and parallel
Surface waves occur at the boundary of two mediums

17. WAVES
PROPERTIES

18. Wave Properties For a sine or transverse wave: Crests – high points
Troughs – low points
Amplitude – distance from the midpoint to the crest (or from the midpoint to the trough)
Wavelength – distance between 2 consecutive pts. of a wave (nm)
Frequency - how often a vibration occurs (Hz)

19. Frequency determines the pitch of the sound
Wave Properties
Frequency determines the pitch of the sound
Amplitude determines how loud or soft a sound seems to be.

20. Wave Properties
Frequency – The number of wavelengths that pass a fixed point each second.
Measured in Hertz (Hz)
For example:
20 vibrations/second is the same as 20 Hz.
150 Hz is the same as 150 vibrations/second.

21. Wave Properties
The wave period is the amount of time it takes for a wavelength to pass a point.
As the frequency of a wave increases, the wave period decreases.
Periods are measured in units of seconds.

22. Wave Properties
The speed of a wave depends on the medium it is traveling through.
It can be calculated using the following equation:
Speed (in m/s) = frequency (in Hz) x wavelength (in m) OR
v = f x λ

23. Wave Interactions Waves can experience four types of interactions
1) Reflection
2) Diffraction
Refraction
Interference

24. Wave Interactions Reflection
­ The bouncing back of a wave as it meets a boundary.
­ Waves reflect at a free boundary
­ When a wave hits a fixed boundary, it is reflected and turned upside down to travel back in the opposite direction

25. Wave Interactions
Diffraction - Bending of a wave as it passes an edge or an opening.
**Stays in the same medium

26. Wave Interactions
Refraction ­The bending of waves as they pass from one medium to another.
**Change mediums.
Example, fish underwater, or looking at fish in an aquarium.

27. Wave Interactions
INTERFERENCE ­This occurs when several waves are in the same location and combine to produce a single, new wave that is different from the original wave.
­Interference of Sound waves creates beats in the music

28. Interference
Wave Interference – When 2 or more waves interact, it results in interference.
Interference can be:
Constructive
Destructive

29. Interference
Constructive Interference ­When the crest of one wave overlaps the crest of another wave, they reinforce each other, and create a wave with an added amplitude.
­Amplitudes are added.

30. Interference Destructive Interference
­When the crest of one wave meets the trough of another wave; they detract from each other, and create a wave with decreased amplitude.
­Amplitudes are subtracted.

31. Interference Standing Waves
­Wave form that appears to not move along the medium
­Creates regions of no vibration (nodes) (Complete destructive interference)
­Creates regions of maximum vibration (antinodes) (Complete constructive interference)