This document provides an overview of waves, including different types of waves and their characteristics. It begins by introducing waves using examples of slinky toys and rope waves. It defines a wave as a disturbance that transfers energy through a medium. The document then covers two types of waves based on direction of movement: transverse waves where particles move perpendicular to wave movement, and longitudinal waves where particle movement is parallel. It also distinguishes mechanical waves that need matter to transmit energy from electromagnetic waves that can transmit through a vacuum. Key wave characteristics like amplitude, frequency, wavelength are explained. Sound waves and light waves are discussed in more detail, noting they are longitudinal and transverse waves respectively.

1. WAVES
Unit 8, Lesson 8.1
By Margielene Judan

2. Lesson
Outline
• Introduction
• Kinds of Waves
• Characteristics of Waves
• Sound Waves
• Light Waves

3. You may not have a scientific
knowledge of waves, but you
probably have a basic notion
of what waves are based on
what you see in everyday life.

7. Have you ever played this?
This is a slinky toy.
When you try to move in in a
forward-backward or up-down
motion, you produce a wave.

8. Also, suppose that you are the girl on the left.
When the man (on the right) propagates the rope
up and down, it creates a wave. The girl, being the
receiver of the wave feels a force.

9. Take note that when the rope is moving, its
particles are only moving in an up-down direction
(see below). Each particle (dot) only moves in a
two-way direction (up-down) not going to the girl.

10. Here, two cases are noted:
1. The girls feels a force coming from the boy.
2. The particle moves in an up-down direction, not
towards the girl.

11. From that, we conclude that…
A wave transfers energy, not mass.
Indeed! You feel a force (it means energy is
propagated/ transferred from the boy to you).
Moreover, no particle is transferred to you (mass).
If that happens, you would gain mass. It’s
absolutely absurd! You cannot get heavier by just
propagating a rope!

12. This leads us to a formal
definition of wave:
“A wave is a simple
disturbance through a
medium in which energy
is transferred.”

13. In the case of our formal
example, the rope is the
medium to which energy is
transferred.

14. Wave pulse – simple disturbance (Figure a)
Wave train – series of disturbance (Figure b)
Figure c is an endless sine wave.

15. KINDS OF
WAVES

16. KINDS OF WAVES
According to the direction of movement
• Transverse Waves
• Longitudinal Waves
According to their ability or inability to transmit energy through
various media.
• Mechanical Waves
• Electromagnetic Waves

17. WAVES ACCORDING TO THE
DIRECTION OF MOVEMENT

18. Transverse Waves
• Movement of particles = perpendicular to the
direction that the wave moves

19. Transverse Waves
• Consider the rope wave earlier. The wave moves
from left to right (large red arrow below), while the
particles move up and down.

20. Transverse Waves
• They form right angles, they are perpendicular.
left-right
up-down

21. Transverse Waves
• Perhaps, you think of waves only in terms of
transverse waves, but there is another kind of
wave.

22. Longitudinal Waves
• Movement of particles = parallel to the direction
that the wave moves

23. Longitudinal Waves
• Movement of particles = parallel to the direction
that the wave moves

25. WAVES ACCORDING TO THEIR
ABILITY OR INABILITY TO TRANSMIT
ENERGY THROUGH VARIOUS MEDIA

26. Mechanical Waves
• Incapable of transmitting energy through a
vacuum (area without matter)
• Needs material such as solid, liquid, or gas to
transmit energy
• Medium = matter
• Ex. water waves, sound waves, earthquake
waves

27. Mechanical Waves
• It is mentioned that sound waves
are mechanical waves.
• The reason behind why two
astronauts cannot hear each other
in space because sound waves
cannot travel in a vacuum (space is
a vacuum).
• Sound waves require matter to be
transmitted. (ex. air)

28. Electromagnetic Waves
• Capable of transmitting energy
through a vacuum
• Termed by physicist James
Clerk Maxwell
• Ex. Light, radio waves,
microwaves, television waves

29. Electromagnetic Waves
• That’s the reason why
sunlight reaches the
earth, because light
doesn’t need a material
medium to transmit
energy.

30. CHARACTERISTICS
OF WAVES

31. CHARACTERISTICS OF WAVES
• Amplitude – maximum distance oved by a particle from its
starting point
• Frequency (f) – number of waves passing through a given
point during the interval of 1 second.
• Wavelength (𝜆) – length of one cycle.
• Wave velocity (𝜈) – speed of wave (𝜈 = 𝜆f)
Other terminologies
• Crests – highest points of a wave
• Trough – lowest points of a wave

32. Transverse Waves
(Crests and Troughs)
Crest Crest Crest
Trough Trough

33. Transverse Waves
(Amplitude – half distance from crest to
trough)
Crest Crest Crest
Trough Trough
Amplitude
Amplitude
Amplitude

34. Transverse Waves
(Wavelength 𝝀 – distance from crest to
crest or trough to trough)
𝝀 𝝀
𝝀 𝝀

35. Transverse Waves
𝝀 𝝀
𝝀 𝝀
Amplitude
Amplitude
Amplitude

36. Longitudinal Waves
(Expansion and Compression)
Expansion
*Amplitude is line density

37. Longitudinal Waves
(Wavelength – distance from compression
to compression; expansion to expansion)
𝝀 𝝀 𝝀
𝝀𝝀

38. SOUND
WAVES

39. Sound
• Form of energy
• Produced when air molecules vibrate and move
in pattern known as waves or sound waves.

40. Sound
• It is a longitudinal wave

41. To make vibrations become sounds, 3 basic elements must be
present:
• Source – produces waves
• Medium – vehicle to w/c sound travels
• Detector or receiver

42. Source
Medium
Receiver

43. https://www.youtube.com/watch?v=JStvGlpucVs

44. Since sound is a
mechanical wave, it only
travels through matter
(solid, liquid, gas).
Depending on the medium,
sound waves travel at
different velocities. In air,
they travel at an average
speed of 343 m/s at 20oC.

45. As seen, sounds travel
fastest in solids, then
liquids, the gases being the
slowest. This is because
molecules in a solid is more
intact, thus, energy could
be transferred easily.
Speed of sound
Solid > Liquid > Gas

46. HOW HUMANS PRODUCE SOUNDS

47. The production of sounds
is attributed to 3 parts:
• Lungs – produce airflow and air
pressure
• Vocal folds within the larynx –
produces the sound by vibrating
• Articulators (tongue, palate, lips)
– articulate and filter the sound
They are all equally important

48. The vocal
cord

49. The vocal cord (open and close position)

50. Length of vocal fold or cord:
• Men – 17 mm to 25 mm
• Women – 12.5 mm to 17.5 mm
The larger the vocal cords, the
lower the pitch of voice.

51. The higher the note, the tenser
and more stretched the vocal
cord.
This would mean that we need to be more
careful when we start to sing higher and
higher notes, as our cord muscles are subject
to more and more strain, and they would then
be more vulnerable to vocal abuse.
Various vocal warmup exercises to stretch
out our vocal cords before singing to prevent
unnecessary harm to our voice.

52. Why do we all have different
quality of sounds?
• Different sizes and shapes
of vocal cords
• Manner from w/c sound is
articulated (trough the
tongue, palate, lips)

53. https://www.youtube.com/watch?v=b89RSYCaUBo

54. DETECTING SOUNDS

55. Our ears detect sounds.

57. Transmission of sound:
1. Outer ear acts as funnel to collect sound
waves.
2. Sound waves reaches the ear drum,
causing it to vibrate.
3. Vibrations are passed from the ear drum
to the 3 bones (hammer, anvil, stirrup)
4. The bones amplify the sound to the
inner ear, which cochlea is found.
5. Cochlea contains fluid that amplifies the
vibration to the auditory nerve.
6. Auditory never sends signals to the
brain.

58. CHARACTERESTICS OF SOUND

60. Acoustics – the science that focuses on the study of
properties and transmission of sound

61. CHARACTERISTICS OF SOUND
• Tone
• Pitch
• Intensity
Differences between sounds are caused by these 3.

62. CHARACTERISTICS OF SOUND
• Tone – depends on the form of the wave
• Pitch – depends on the frequency of the wave
• Intensity – depends on the amplitude of the wave
We will tackle this in more detail in the following slides.

63. Tone
• Refers to sound quality
• depends upon the form of the waves
• Most sounds are not pure tones. Most are combinations of two
or more tones (image below).

64. Wind Trio
String Quartet
Orchestra
Piano
These are the sound waves produced by different instruments. Note that they
all have the same pitch, but a different tone. (Press the play button to play.)

65. Pitch
• Refers to subjective impression
about the “highness or
lowness” of a tone
• depends upon the frequency of
the waves
• Sound waves of the same
frequency are of the same pitch.
• High frequency= high notes
• Low frequency = low notes

68. Pitch
• The human ear can hear sound of
different frequencies. It usually varies
with a person, usually with age. The
audible range for humans is 20 to
20,000 Hz (hertz). Younger individuals
tend to hear a wider range of
frequencies waves.
• Some animals (dogs, bats, dolphins)
can hear higher frequencies (above
20,000 Hz). They use it for sensing their
environment and navigation.

69. Pitch
• Ultrasonic – frequencies above 20,000 Hz
• Infrasonic – frequencies below 20 Hz
Name Frequency Range Characteristics
Infrasonic 0-20 Hz Ear cannot detect, but can be felt as
vibrations.
Sonic (or Audio) 20 – 20,000 Hz Normal range for human ears
Ultrasonic 20,000 + Hz Humans cannot detect, although some
animals hear part ways into this range; also
used in medicine

70. Intensity
• Amount of energy that is
transported in a given area
per unit time.
• depends upon the amplitude
of the waves

71. Intensity
• Related to loudness, but
different in meaning.
• Intensity is the amount of
sound energy in a wave
• Loudness is the sensation on
the ear that the intensity
produces
• High amplitude = louder
sound

74. Intensity
• Measured through the
decibel system (dB).

75. Decibel system (dB)
• Works logarithmically, meaning:
• 10 dB is 10x as intense as 0 dB.
• 20 dB is 100x as intense as 0 dB.
• 30 dB is 1,000x as intense as 0 dB.
• 40 dB is 10,000x as intense as 0 dB.
• etc…
• The normal intensity is 71-90 dB, equivalent to regular daily
sound like people talking.

76. Let’s compare the effects of changing the amplitude and frequencies on the
“Minions Banana Song”. (Click the play button). Notice the differences in the
wave forms.
Normal Amplitude
Larger Amplitude
Smaller Amplitude

77. Let’s compare the effects of changing the amplitude and frequencies on the
“Minions Banana Song”. (Click the play button). Notice the differences in the
wave forms.
Normal Frequency
Higher Frequency
Lower Frequency

78. Music and Noise
• Some sounds are music to the ears, while others are
considered noise.
• Noise is a more irregular sound wave.

79. LIGHT
WAVES

80. In terms of the ability or inability of a wave to travel
in a material medium (solid, liquid, gas), we have
classified waves into:
1. Mechanical waves – needs material medium
2. Electromagnetic waves – can travel in a
vacuum

81. Sound is an important example of mechanical
wave. Without a material medium (ex. air), we
would not be able to hear each other.

82. Another important wave we will study in this
chapter, is the light wave, which is an
electromagnetic wave.

83. Light
• Form of electromagnetic wave
• Responsible for the sense of
sight
• Travels a speed of 300,000,000
m/s, 3 X 108 m/s to be short.
• Exists as both a particle and a
wave.

84. NATURE OF LIGHT

85. NATURE OF LIGHT
(Pre-history)

86. Plato
• Thought that light is emitted by the eye
• Supported by Euclid
• Contradicted by the Pythagoreans
Empedocles
• Forerunner of Plato
• Light is composed of high speed waves

87. NATURE OF LIGHT
(Development)

88. Two theories were developed on the basic nature
of light:
• Wave Theory or Undulatory Theory
• Corpuscular or Emission Theory

89. Wave Theory
• Light is a wave.
• Light has a wave motion.
• It starts from a vibrating body (source) and is transmitted at high
speeds.

90. James Clerk Maxwell
• Established the wave theory
• He constructed an oscillating
electrical circuit which showed that
changing electric and magnetic
fields could produce
electromagnetic radiation that could
travel through a vacuum.

91. Heinrich Hertz
• Proved that light is
electromagnetic. It could
travel in a vacuum.
• Showed existence of another
kind of electromagnetic wave,
the radio wave.

92. Christian Huygens
• Supported the wave theory
• Light can travel through a
vacuum (without matter),
which they called ether.

93. Sir Isaac Newton
• Contradicted the wave
theory
• Proposed the
Corpuscular or
Emission Theory

94. Corpuscular or Emission Theory
• Light is a stream of particles.
• It travels only in straight lines called rays, and not like waves.

95. Sir Isaac Newton
• One thing he observed is that light undergoes refraction
(changes direction) upon hitting the water. He hypothesized that
light must be an atom-like particle that changes its direction
when it hits a medium with different density.

96. Sir Isaac Newton
• However, long after his death in the 19th century, he was
proved wrong by saying that light is like an atom particle.
• When two light rays/beams intersect, they do not change
direction (refract).

97. Albert Einstein
• Observed the photoelectric
effect and supported the
Emission Theory.
• Said that light is a stream of
particles called photons, which
are bundled in discrete
quantities called quanta.

98. Corpuscular or Emission Theory
• The wave theory cannot explain a certain phenomenon, called
the photoelectric effect. It can only be explained by the
emission theory which supports that light must be a particle.

99. Photoelectric Effect
• Emission of electrons from a metal plate

100. Scientists were puzzled for hundreds of years regarding
the true nature of light (particle or wave?)

101. NATURE OF LIGHT
(Modern History)

102. Louis Victor de Broglie
• Proposed that every particle of
matter is somehow endowed with a
wave to guide it as it travels.
• Hence, the particle-wave duality
of light was born.

103. Particle-Wave Duality of Light
• Solved all the problems of whether light is a wave or a particle.
• Light acts as a wave and a particle.

105. ELECTROMAGNETIC SPECTRUM

106. Electromagnetic Spectrum
• A range of electromagnetic waves
• Arranged according to their frequency or wavelength.

108. Electromagnetic Spectrum
• The colors we see (ROYGBV) is only part of the EM spectrum.
• Arranged from lowest to highest frequency (highest to lowest
wavelength) is seen from left to right (see below)

109. Visible Spectrum
• Red has the longest wavelength (smallest
frequency)
• Violet has the shortest wavelength (largest
frequency)
• Indigo is not anymore distinguished as a
separate color. Thus, we have “ROY G BV”
rather than “ROY G BIV”.

110. Assignment (1 whole sheet of paper):
• Research and enumerate the uses of each electromagnetic
wave: from radio waves up to gamma rays. Keep it short only
Ex.
Infrared – Infrared thermometers
X-ray – radiologic x-ray
Microwaves – cooking
• Answer the Unit Test on page 288-289: Check Your Knowledge
and Check Your Understanding.

111. LIGHT SOURCES AND
PROPAGATION

112. Luminous objects
• Emit or send off their own light
• Radiate heat and store their own
energy
• Ex. sun, starts, fire, lasers,
lamps, light bulbs

113. Nonluminous objects
• Cannot emit or send off their
own light
• They only reflect light like the
moon, which reflects light
from the sun.
• Ex. moon, cars, buildings,
people

114. Photometry
• Deals with the measurement of visible light
• Brightness is measured through luminous intensity
expressed in candela (cd) units.

115. When light waves encounter any substance, they may
either be:
• Transmitted
• Refracted
• Reflected
• Absorbed

116. Transmission
• Passes through a substance or object

117. Refracted (refraction)
• Light changes direction upon passing through a different medium with
different density (like passing a laser from air to water; it will change
direction as seen below because water has different density than air)

118. Reflected (Reflection)
• Bounces back to the same angle

119. Absorbed
• Not transmitted; absorbed rays are not seen anymore

120. Why are leaves green?
-It reflects green light while it
absorbs the rest of the colors
(red, yellow, blue, violet). The
color of the chlorophyll inside the
chloroplast is green.
This applies to all colors seen.

121. Special colors that we
perceive are:
• Black – the absence of color
• White – the combination of
all colors
In black, all colors are absorbed,
nothing is reflected.
In white, all colors are reflected,
nothing is absorbed.

122. That’s the reason why
wearing dark colors during
warm days is discouraged.
In dark colors, more light
waves are absorbed,
meaning more heat is
absorbed too.

123. Objects are classified in terms of the way they allow light
to pass through:

124. Transparent
• Allow light to pass through clearly

125. Opaque
• Doesn’t allow passage of light; blocks light

126. Translucent
• Allow only some
amount of light to pass
through, resulting in a
blurred figure.
• Have both the
characteristics of
transparent and opaque
objects

127. Laboratory 4.1 – 4.3 tomorrow
• Each group will be performing different experiments, as will be
shown in the following slides.
• Each group must document their experiment. Bring a camera.
• Present the concept and the results on the next day by a
powerpoint presentation. Show actual pictures. Be creative
• The day after the presentation, the leader will pass to me a
written or type-written report about the contribution of each of
his/her members. Each member will be rated from 1-10.
• The members will also rate their other groupmates, including
the leader.

128. Laboratory 4.1 – Group Evaluation
• Criteria:
Content of Written Evaluation by the Leader 40%
Evaluation from the Leader 25%
Evaluation from the Members 25%
Promptness in Submission 10%
(You’ll get a perfect 10% if the leader passes the
report on time during the next science class)
Total 100%

129. Laboratory 4.2
• Answer the answer sheet for your experiment. It will be graded
accordingly.

130. Laboratory 4.3 – Group Presentation
• Criteria:
Content and Delivery 30%
Technicality (must be able to explain 30%
well the scientific principles involved)
Creativeness 20%
Documentation (must show actual pictures 10%
of the performed experiment)
Visual Aids (video, props, etc.) 10%
Total 100%