Waves transfer energy through a medium by causing a disturbance that moves through the medium without the medium itself moving; there are mechanical waves which need a medium and electromagnetic waves which do not. Mechanical waves include sound waves and ocean waves, while electromagnetic waves include visible light, radio waves, x-rays and more, and all waves can be characterized by their wavelength, frequency, amplitude, and speed which depends on the medium.

2. Essential Question?
• How does a wave transfer energy?

3. Waves
• Wave – a disturbance that carries energy
through matter or space
• For an example;
• Ocean waves disturb water and transfer energy
through
• During an earthquakes, energy transferred in
powerful waves that travel through the earth
• Light is a type of wave that can travel through an
empty space from one place to another.

4. Wave – a disturbance that
carries energy through matter
or space
Mechanical waves –require a
medium to travel through

5. Medium – something that
something travels through
Sound travels through air,
therefore, air is the medium.
Waves in a pond travel
through water, therefore,
water is the medium.

6. Waves
1. You have learned how Newton's laws of
motion and principles of conservation of
energy govern the behavior of particles.
2. These laws and principles also govern the
motion of waves.
3. There are many types of waves that
transmit energy even the ones you
cannot see.

7. • Mechanical Waves - A mechanical wave is a
disturbance that travels through some material
or substance called the medium for the wave.
• Note: The medium as a whole does not travel
with the wave.
• Note: A wave transfers energy, but it does not
transfer any material or substance outward from
the source.

8. Waves carry energy because
they can do work.
Water waves can move an object
up and down or throw it on a
beach.
Sound waves move your eardrum
and you hear.
Light waves allow your eye to see
and can make an image on film.

9. Most waves are caused by a
vibration.
Particles in a medium can vibrate
either up and down or back and
forth.
Waves are classified by the
direction that the particles in the
medium move as a wave passes
by.

10. Wave Phenomenon
• Wave phenomenon, energy can move
from one location to another, yet the
particles of matter in the medium return to
their fixed position. A wave transports its
energy without transporting matter.

11. Two types of Waves
• Transverse waves
• Longitudinal wave

12. 2. Longitudinal wave – particles
vibrate parallel to the direction
of the wave motion

13. Sound Waves
• A sound wave traveling through air is a
classic example of a longitudinal wave.

14. 1. Transverse waves – particles
move perpendicular to the motion
of the wave

15. Transverse waves
• Waves in the electromagnetic spectrum
are Transverse Waves

16. Parts of a Transverse
Wave
Wavelength
Crest Crest
Normal
Amplitude
Trough Trough
Wavelength

17. Parts of a Wave
• Crest - each high point of a wave
• Trough – each low point
• Wave length – distance between points
where the wave pattern repeats itself
• Amplitude – any periodic motion, the
maximum distance an object moves from
equilibrium

18. Parts of a Longitudinal
Wave
Rarefactions
Compressions

19. Rarefactions
• Rarefactions - are regions of low air
pressure Rarefactions
Compressions

20. Compressions
• Compressions are regions of high air
pressure Rarefactions
Compressions

21. The difference between
Transverse and Longitudinal
waves
• Transverse waves -are those in which
displacement of particle is perpendicular
to that of propagation of wave.
• Longitudinal waves - are those in which
displacement of the particle is in a
direction parallel to that of propagation.

22. Period – In a periodic motion, the amount of
time required for an object to repeat one
complete cycle
Periodic motion- wave move up and down
at the same rate
PERIOD
Example: 1 wave every 20 seconds

23. Frequency – The number of wave crest that
pass a point during one second.
( expressed in hertz)
Example: 3 waves per Second (3Hz)

24. Frequency Equation
• The frequency of a wave length is equal to
the reciprocal of the period
• F=1/T

25. Hertz
• The symbol for frequency is f.
• The SI unit is hertz (Hz).
• One vibration/wave per second is 1 Hz.
• Two vibrations/wave per second is 2
Hz.

26. Wave length Equation
• The wavelength of a wave is equal to the
velocity divided by the frequency
• Wavelength = V/f

27. Period & Frequency
Depends on?
The source
Does Not depend on?
The medium and wave’s speed

28. What affects the waves speed?
The speed of a wave depends on the
medium in which the wave is traveling.

29. Light waves can move
through air faster than they can
move through water. This is why a
pencil will look broken when it is
placed in a glass of water.
Exactly where does the pencil
look broken?
At the junction of the two different
mediums.

30. Sound travels faster in
water than in air. Sound travels
faster in solids than in liquids.
Why do you think this is so?
The closer the molecules are, the
easier it will be for the molecules
to bump into one another. This
allows the vibrations to move
faster, thus allowing the wave to
move faster.

31. Comparing Light & Sound Waves
• Light waves can move through air faster than
they can move through water. Because?....
• Once the Light Wave enters another medium it
changes directions and slows down.
• Sound travels faster in water than in air.
Because?....
• The closer the molecules are, the easier it will be
for the molecules to bump into one another.
This allows the vibrations to move faster, thus
allowing the wave to move faster.

32. Doppler Effect
Doppler effect – a change in the
frequency of a wave when the source
or observer is moving

33. Reflection
• bouncing back of a wave when it meets
a surface

34. Refraction
• the bending of waves as they pass
from one medium into another

35. Diffraction
• bending of waves as they pass through
narrow openings or around sharp corners

36. Interference
• Interference – the combination of two
or more waves that exist in the same
place at the same time

37. Interference Waves
• Interference of light is difficult to observe since
the waves are so small and the vibrations so
rapid.
• However, interference takes place with any kind
of wave motion, and the effects of interference
can be more easily seen by the examining the
behavior of water waves, which are in many
ways similar to light waves, but travel more
slowly and are more easily noticeable.

38. Constructive interference
Constructive interference – waves
combine to make a larger wave

39. Destructive interference
• Destructive interference – waves
combine to make a smaller wave

42. Interference – the combination of
two or more waves that exist in the
same place at the same time
Constructive interference – waves
combine to make a larger wave
Destructive interference – waves
combine to make a smaller wave

43. Review
• Mechanical waves (sound, ocean waves,
seismic) require a medium (air, water,
ground) to travel through.

44. Electromagnetic Waves
Electromagnetic waves – waves that are
caused by a disturbance in electric and
magnetic fields and does not require a
medium to travel through
Electromagnetic waves are produced by
the vibration of charged particles

45. Electromagnetic Waves

46. Electromagnetic Waves
• Electromagnetic waves are created by the
vibration of an electric charge.
• This vibration creates a wave which has
both an electric and a magnetic
component.
• An electromagnetic wave transports its
energy through a vacuum at a speed of
3.00 x 108 m/s (a speed value commonly
represented by the symbol c).

47. Examples of electromagnetic waves:
Lower energy
Radio waves
Longer wavelength
Microwaves
Infrared waves
Visible light waves
Ultra-violet waves
Higher energy
X-rays Shorter wavelength