2. Topic Outline
1. Motion
a. Displacement
b. Distance
c. Speed
d. Velocity
e. Acceleration
f. Motion Detectors
2. Waves
a. Nature and Characteristics of Waves
b. Classification of Waves
i. Nature: Mechanical and Electromagnetic Waves
ii. Vibration of Particles: Longitudinal and
Transverse
3. Sound
a. Nature and Production of Sound
b. The Characteristics of Sound
i. Pitch
ii. Loudness
iii. Quality
c. The Perception of Sound
4. Light
a. Nature and Theories about Light
b. The Rectilinear Propagation of Light
c. Colors, Speed, and Intensity of Light
5. Heat
a. Heat
b. Methods of Heat Transfer
i. Conduction
ii. Convection
iii. Radiation
6. Electricity
a. Origins of Electricity
b. Electric Charges
c. Conductors: Semiconductors and
Superconductors
d. Insulators
e. Processes of Charging
i. Friction
ii. Conduction
iii. Induction
f. Grounding
3. Grading System
Subject Requirements
Expectations and Learning Opportunities
As per DepEd Order 8 (s. 2015), Policy Guidelines on Classroom Assessment for the K to 12 Basic Education
Program
❏ Exit Tickets (3-4)
❏ Seatworks (6-10)
❏ Homeworks (2-3)
❏ Participation: Recitation and Notebook
❏ Quizzes (2)
❏ Performance Task Activities (2-4)
❏ Quarterly project (1)
❏ Quarterly exam (1)
4. Throughout the journey…
Expectations and Learning Opportunities
❏ Secure a pass (clinic, errand, or restroom pass) before you leave the classroom
for a while
❏ Raise your hand if:
➢ You have concerns
➢ You want to answer the question
✓ Wait to be acknowledged and take turns on listening and speaking.
❏ Submit your works on time. Notes are graded.
❏ If concern arises, talk to your teacher beforehand.
➢ After-school communications are open until 7PM via Facebook
Messenger/ Google Mail.
5. On Exit Tickets…
Expectations and Learning Opportunities
✓ An exit ticket should be accomplished every after core lessons
➢ This is to check your comprehension via metacognition.
➢ Exit tickets are to be checked every after core lesson.
➢ Leave your science notebook on top of/in your class cabinet.
❏ The following should be handwritten (notebook):
➢ Answers in Pause, Think, and Recall (Items will be flashed on the screen)
➢ Summarize the discussion in three to five sentences
➢ Which part(s) of the lesson do I have difficulty(-ies) with?
○ What could I do about that (those)?
○ How can I be helped (if applicable)?
➢ One Question about today’s discussion
✓ You’ll be given 10 minutes before the end of the lesson to finish.
6.
7. HOMEWORK 1
● On your notebook, define the following terms and infer how
they are used in real life:
○ Displacement
○ Distance
○ Speed
○ Velocity
○ Acceleration
Deadline: January 13, 2023
9. 7TH GRADE
OBJECTIVES
1 define what
is force and
its types 3
2
discuss
examples of
the types of
forces
imitate
examples of
the types of
forces that
they have
seen from
their
environment
12. DEMONSTRATE
Get your Science
Notebook and your pen.
Then, put them on your
armchair desk
Did your
notebook and
pen fell on the
ground when
you placed
them on top of
your desk?
14. FORCE
● A force may also
be defined in
terms of how it
can change the
state of motion
of an object.
15. FORCE: CONTACT FORCES
● Contact forces are forces that require direct contact between two
bodies.
● Frictional force, normal force, and applied force are examples of
these forces.
16. FRICTIONAL FORCE (Ff)
● any force that opposes the
relative motion between
objects or systems in
contact.
FORCE: CONTACT FORCES
For example, if a school
bag is being dragged
across the floor, the floor
exerts a frictional force in
a direction opposite to the
motion of the bag.
17. APPLIED FORCE (Fa)
● a force directed to an object
by a person or another
object.
FORCE: CONTACT FORCES
For example, the man pushes
the cart along the road. The
applied force in this situation
is the force exerted on the
cart by the man and vice
versa.
18. NORMAL FORCE (Fn)
● the support force exerted on
an object by a surface it is in
contact with.
● Note that normal force is
always perpendicular to the
surface that the object is
resting on.
FORCE: CONTACT FORCES
For example, the book
experiences a normal force
exerted by the surface of the
table.
19. FORCE: NONCONTACT FORCES
● Forces that do not involve direct physical contact between
two bodies are called noncontact forces.
● Gravity, electromagnetic force, and nuclear forces are
examples of noncontact forces.
20. GRAVITATIONAL FORCE (Fg)
● the force of attraction
between objects by virtue of
their masses
● pulls objects toward the
center of Earth.
FORCE: NONCONTACT FORCES
For example, falling of dry leaves
to the ground
21. ELECTROMAGNETIC FORCE
● the force responsible for the
attraction and repulsion of
charges.
FORCE: NONCONTACT FORCES
For example, electronic
equipment, such as the
television and integrated
circuits in appliances
22. NUCLEAR FORCE
● the force that holds the
protons and neutrons within
the nucleus
FORCE: NONCONTACT FORCES
23. We like to move it,
move it!
Identify the force/forces that are present on the
following scenarios and explain why.
1. Riding a bicycle
2. Rolling ball on a flat
surface
3. Cathode-ray
televisions
4. Standing on a flat
surface
5. Pushing the switch
to turn a light on or
off
6. Rolling rock from a
hill
7. Mug on the table
8. Person rubbing a
balloon against
his/her hair
9. Falling coin
10. Dragging a Chair
24. HOMEWORK 1
On your notebook, define the following terms:
★ Displacement
★ Distance
★ Speed,
★ Velocity, and
★ Acceleration
Deadline: January 11, 2023
31. IN ONE PHRASE, SHARE YOUR
ANSWERS FROM YOUR
ASSIGNMENT
DISTANCE
DISPLACEMENT
32. Distance is a scalar
quantity, while
displacement is a
vector quantity.
33. DISTANCE
● Distance, represented as d, refers to the actual length of path taken
by an object in moving from its initial position to its final position.
34. DISPLACEMENT
● Displacement d refers to the straight-line distance between the
initial and final positions, with the direction pointing toward the final
position.
37. 7TH GRADE
OBJECTIVES
1 infer the
concept of
motion
2
describe
motion in
terms of
distance,
displacement,
and speed
38. SPEED
● Speed is the quantity used to describe the distance traveled per unit
time.
● Speed essentially describes the rate of change of position. Speed
does not indicate the change in direction. Hence, it is a scalar
quantity.
39. Speed: Units
To calculate speed, you need to consider any of the following combinations
of units for distance with respect to time:
● kilometers per hour (km/h or kph),
● centimeters per second (cm/s),
● meters per second (m/s),
● centimeters per day (cm/day).
41. Instantaneous Speed & Average Speed
● The speed of a car at a particular time is called its instantaneous
speed
● Average speed indicates the average rate of movement during the
entire time of travel throughout the entire distance traveled.
○ where:
⊽= average speed
Δd=total distance traveled
Δt=total time traveled
42. Sample Problem
A cheetah can travel 625m in 25s. What is its average
speed?
G A F S&A
d=625 m
t= 25 s
⊽=?
43. Sample Problem
How far can the cheetah in the previous problem
go in 1 min?
G A F S&A
⊽= 25 m/s
t= 1 min= 60s
d=?
44. GROUP ACTIVITY: METERS PER SECOND
The students will be grouped into three. Each member shall participate in a back-and forth
walk.
Each group should record their data as follows:
Then, answer the following questions:
1. Who walked the fastest? By how much?
2. Who walked the slowest? By how much?
Student’s name Distance (m) Time (s) Speed (m/s)
6m To compute:
45.
46. STOP
Information beyond this slide needs to be updated
(additional information, adding examples, and activities)
48. 7TH GRADE
OBJECTIVES
1 reiterate the
concept of
motion
2
describe
motion in
terms of
velocity
3
solve word
problems
involving
velocity
49. Velocity
Velocity is the displacement per unit of time; the directional speed of an
object in motion.
50. Sample Problem
A plane takes off from Manila at 5:30 am, and is expected to
land in Zamboanga City, which is 852 km south of Manila, at
exactly 7:00 am. What should be the average velocity of the
plane for it to land in Zamboanga City on time?
G A F S&A
d= 852 km,
south of Manila
t= 1h and 30
minutes or 1.5h
v=?
51. Sample Problem
A motorbike cruises northward down a straight highway at a
constant velocity of 10 m/s for 30s. What is the displacement
of the motorbike?
G A F S&A
v= 10 m/s,
north
t= 30s
d=?
55. 7TH GRADE
OBJECTIVES
1 reiterate the
concept of
motion
2
describe
motion in
terms of
acceleration
3
solve word
problems
involving
acceleration
56. ACCELERATION
● Acceleration a is defined as the rate of change of velocity with time,
and usually measured in meters per second squared (m/s2).
Where:
a: acceleration
vf: final velocity
vi: initial velocity
T: time
57. ACCELERATION
● A freely falling ball accelerates
toward the ground at a rate of
9.8 m/s2 that is to say, the
velocity of the falling ball
increases by 9.8 m/s2 every
second.
● Physicists have determined
9.8 m/s2 as the constant value
of acceleration due to Earth's
gravity
58. ACCELERATION
Positive Acceleration
If the direction does
not change,
acceleration is said to
be positive (+) if the
speed increases
Negative Acceleration
If the direction does
not change,
acceleration is said to
be negative (-) if the
speed decreases
Zero Acceleration
If the direction does
not change,
acceleration is said to
be zero if there is no
change in speed
59. Sample Problem
Martin rides a bicycle at 1.5 m/s south. After 10 s, he is
pedaling at 3.0 m/s south. What is his acceleration?
G A F S&A
vi = 1.5 m/s
vf = 3.0 m/s
t= 10 s
a=?
60. Sample Problem
A truck accelerates uniformly from rest to 35 m/s in 30 s.
It travels in only one direction. Find (a) the magnitude of
the acceleration of the truck and (b) the distance it
traveled.
G A F S&A
vi = 0 m/s
vf = 35 m/s
t= 30 s
a=?
A
B
61. Practice Problem
A car travels 24 m/s due cast in 30 s. Assuming the car
starts from rest, what is its acceleration?
G A F S&A
vi = 0 m/s
vf = 24 m/s
t= 30 s
a=?
62. HOMEWORK 2
On a short (8.5x11) bond paper, answer the problem set: Follow
the GAFS&A format.
Speed
If a driver takes 30 min to get to the town market,
which is 1.5 km away from his house, what is his
average speed?
Deadline: January 25, 2023
1
63. HOMEWORK 2
On a short (8.5x11) bond paper, answer the problem set: Follow
the GAFS&A format.
Velocity
Solve for the
missing
values
v (m/s) d (m) t (s)
1 20.0 ? 10.0
2 ? 20 120.0
3 47.2 1660 ?
4 ? 41.5 17.6
5 8.4 ? 100.0
Deadline: January 25, 2023
2
64. HOMEWORK 2
On a short (8.5x11) bond paper, answer the problem set: Follow
the GAFS&A format.
Acceleration and Distance
Michael Schumacher, a German racing driver,
accelerates his race car uniformly from 18.2 m/s to
48.2 m/s in 2.45 s.
Determine the magnitude of his car and the
distance traveled.
Deadline: January 25, 2023
3
72. What is the disturbance that travels through a
medium or a vacuum and carries energy?
3
73. Wave, Wave Pulse, and Wave Train
● A wave is a disturbance
that travels through a
medium or a vacuum and
carries energy.
● A single, non repeated
disturbance is called a
wave pulse.
● A succession of periodic
disturbances is called a
wave train or periodic
wave.
74. What are the five (5) Characteristics of a
Wave?
Hint: F, P, W, S, and A
4-8
75. Characteristics of Waves
Waves can be described in terms of frequency, period,
wavelength, velocity or speed, and amplitude.
76. What do you call the number of waves
produced per unit time?
9
77. Characteristics of Waves
● The frequency, f of a
wave is the number of
waves produced per
unit time.
● It also refers to how
often the particles of a
medium vibrate when a
wave passes through it.
● The SI unit of frequency
is the hertz (Hz).
78. What do you call the time taken for one
complete cycle of the wave to pass a
reference point?
10
79. Characteristics of Waves
● The period, T of a
wave is the time
taken for one
complete cycle of the
wave to pass a
reference point.
● Period, is expressed
in units of time,
usually in seconds.
80. What do you call the distance between any
two successive points in a wave that are in
phase with each other?
11
81. Characteristics of Waves
● Wavelength, 𝝀 is
the distance
between any two
successive
points in a wave
that are in phase
with each other
82. Characteristics of Waves
● Speed, v is the distance traveled by a wave per unit time.
This equation is known as the
basic wave equation.
83. What do you call the maximum amount of
displacement of a particle on a medium from
its resting position?
12
84. Characteristics of Waves
● The amplitude, A of a wave refers to the maximum amount
of displacement of a particle on a medium from its resting
position.
● The greater the amplitude, the greater the energy carried by
the wave.
87. Mechanical waves require a
medium to propagate.
Electromagnetic waves can
travel in a vacuum and in
any medium.
88. What are the directions of vibration of the
particles in a wave?
14
89. Direction of Vibration of the
Particles
According to the direction of vibration of the particles, waves may be
longitudinal or transverse.
90. Direction of Vibration of the
Particles
● In a transverse
wave, the particles
of the medium are
vibrating
perpendicularly to
the direction of
wave propagation
and are made up of
alternating hills and
valleys. The top of the hill is called crest, while the bottom of
the valley is called trough
91. Direction of Vibration of the
Particles
● A longitudinal wave
is where the
particles of the
medium vibrate
parallel to the
direction of the
wave propagation.
Longitudinal waves are composed of compressions, where particles of the
medium are closer together, and rarefactions, where they are apart
94. 7TH GRADE
OBJECTIVES
1 describe
what is the
electromagn
etic
spectrum
2 discuss the
nature of
gamma rays,
X-rays,
ultraviolet
radiation,
visible light,
infrared
radiation, and
radio waves
96. Characteristics of Waves
● All
electromagnetic
waves propagate
in a vacuum with
a speed of
299,792,458 m/s
or 3×108 m/s.
This speed is
usually
represented by a
small letter c.
97. List down the seven regions of the
electromagnetic spectrum.
16-22
98. The Electromagnetic Spectrum
● The electromagnetic spectrum refers to the range of all
types of electromagnetic radiation.
● Electromagnetic radiation is a form of energy that travels
through space as a wave and includes radio waves,
microwaves, infrared radiation, visible light, ultraviolet
radiation, X-rays, and gamma rays.
101. Radio Waves
● Discovered by
Heinrich Hertz in
1887.
● They are the
longest of all
electromagnetic
waves, which
range from 10-1 to
104 m.
GIFs from: Stickman Physics. (n.d.). Waves of the Electromagnetic
Spectrum.http://stickmanphysics.com/stickman-physics-home/electromagnetic-
waves/waves-of-the-electromagnetic-spectrum/
102. Uses of Radio
Waves
Radio
Radio Frequency
Identification (RFID) tags
Bluetooth Wi-Fi
Radio waves are
classified into long and
medium waves used
by amplitude
modulation (AM)
stations, very high-
frequency (VHF) used
by frequency
modulated (FM)
stations, and ultra
high-frequency (UHF)
104. Microwaves
● Discovered by
Maxwell in 1864.
● They have short
wavelengths,
ranging from 10-3
to 10-1 m, and are
easily absorbed by
water molecules.
GIFs from: Stickman Physics. (n.d.). Waves of the Electromagnetic
Spectrum.http://stickmanphysics.com/stickman-physics-home/electromagnetic-
waves/waves-of-the-electromagnetic-spectrum/
105. The Microwave
Oven
A microwave oven uses
2.45 GHz microwaves to
cook food. These
microwaves transfer the
water molecules in the
food. Plastic food
containers are usually
used when heating or
cooking in a microwave
oven because plastics
are heat-resistant.
106. Infrared Rays
● Discovered by
British- German
astronomer Sir
William Herschel
in 1800.
● Their wavelengths
range from 10-7 to
10-3 m.
GIFs from: Stickman Physics. (n.d.). Waves of the Electromagnetic
Spectrum.http://stickmanphysics.com/stickman-physics-home/electromagnetic-
waves/waves-of-the-electromagnetic-spectrum/
108. Uses of Infrared Waves
Burglar Remote
Systems
Night Vision
Equipment
TV Remote
Control
109. Visible Light
● Light is the part of the
electromagnetic
spectrum that is
visible to the unaided
eye.
● It extends from the
shortest wavelength
(violet) to the longest
wavelength (red)
GIFs from: Stickman Physics. (n.d.). Waves of the Electromagnetic
Spectrum.http://stickmanphysics.com/stickman-physics-home/electromagnetic-
waves/waves-of-the-electromagnetic-spectrum/
111. Components of Visible Light
Color of Light Wavelength
Red 700 nm
Orange 610 nm
Yellow 590 nm
Green 550 mn
Blue 470 mn
Violet 380 nm
112. Ultraviolet Rays
● Discovered by Johann
Wilhelm Ritter
● Their wavelengths
range from 1x10-8 to
4x10-7 m.
GIFs from: Stickman Physics. (n.d.). Waves of the Electromagnetic
Spectrum.http://stickmanphysics.com/stickman-physics-home/electromagnetic-
waves/waves-of-the-electromagnetic-spectrum/
114. Uses of Ultraviolet Rays
UV rays are used to
detect forged bank
notes and render
visible the security
marker ink in
signatures on
bankbooks. The UV
rays can also be
used to sterilize
medical equipment.
The Philippine Bills: The Palm Civet on the ₱20, Giant Trevally on the ₱50, Whale Shark
on the ₱100, Philippine Tarsier on the ₱200, Blue-Naped Parrot on the ₱500, and South
Sea Pearl on the ₱1,000
115. X-Rays
● Discovered by Wilhelm
Conrad Roentgen
● Their wavelengths
range from 1x10-11 to
4x10-7 m.
GIFs from: Stickman Physics. (n.d.). Waves of the Electromagnetic
Spectrum.http://stickmanphysics.com/stickman-physics-home/electromagnetic-
waves/waves-of-the-electromagnetic-spectrum/
117. Uses of X-Rays
Soft X-rays can
penetrate soft
substances such as
flesh and bones,
Hard X-rays, which
are more
penetrating, are used
mainly in industries.
Aside from taking
photographs of the
internal body parts,
X-rays are also used
in airport security
checks to see the
inside of luggage.
118. Gamma Rays
● Discovered by Paul
Villard in 1900
● These are emitted by
radioactive materials
such as cobalt-60 and
cesium-137.
● They are the shortest
of all electromagnetic
waves. Their
wavelengths range
from 10-14 to 10-11 m. GIFs from: Stickman Physics. (n.d.). Waves of the Electromagnetic
Spectrum.http://stickmanphysics.com/stickman-physics-home/electromagnetic-
waves/waves-of-the-electromagnetic-spectrum/
120. Uses of Gamma Rays
Gamma rays are
used to detect
cracks in metals.
While they can
cause cancer and
even mutation,
they can also
destroy cancer
cells in a process
called
radiotherapy.
127. Excuse me, what song
are you listening to?
A. Each student will recommend a
song until a playlist is made.
B. Students will listen to each
song. Observations will be made
by how they can hear the
delivery of:
a. Beat
the underlying pulse or
rhythm that drives a piece
of music forward
a. Voice & Lyrics
the vocal expression of a
human performer
a. Instruments
devices or tools used to
create musical sounds
The G7 Playlist
Song Title Artist Recommended by
Duda Zild Ashley
Lover, You Should've Come
Cver
Jeff Buckley Mishka
About You The 1975 Caly
Girl in the Mirror Sophia Grace ft.
Silento
Jia
Silver Lining The Neighborhood Chanel
黒鉄たま (CV: 秋奈) - いただき
バベル (Aiobahn Remix)
Aiobahn Rainne
Apparently (Clean) J. Cole Marc
The Night We Met Lord Huron T. Mari
128. What is Sound
● Sound is a
longitudinal wave
that is created by
vibrating objects.
It is a mechanical
wave; requires a
medium to
propagate, thus it
cannot travel in a
vacuum.
129. The forward vibration of the prongs
pushes the air molecules to the right and
compresses them. This is called
compression or condensation.
As the prongs move back, they produce a
region of decreased density and pressure.
This region is called rarefaction.
Sound and Tuning Fork
130. Sounds that are heard every day
may be classified as either musical
tone or noise. A musical tone is
produced by regular vibrations,
while noise is produced by irregular
vibrations.
131. Production of Sound
● The vibration
of the vocal
cords in the
larynx
produces the
human voice.
Your vocal cords are inside your voice box
(larynx), which is on top of your windpipe
132. Production of Sound
The buzzing sound of bees, for
example, is produced by the rapid
movement of their wings against air.
Musical sounds can be made by tapping
percussion instruments, plucking stringed
instruments, or blowing air through wind
and brass instruments.
134. Characteristics
of Sound
Pitch
● Pitch is the
highness or
lowness of a
sound. It
depends on the
frequency of the
sound produced
by an object..
A high- pitched sound must be a high-frequency sound
consisting of short waves, while a low-pitched sound must
be a low-frequency sound made up of long waves.
135. A change in voice pitch happens in
both males and females during
puberty.
136. Puberty and Male Voice
● The larynx gets
bigger, and the
vocal cords
become longer and
thicker.
● As the body
adjusts to these
changes, the voice,
especially of
males, cracks or
squeak.
Also, as the larynx of a male grows, it tilts to a different
angle inside the neck, forming a lump known as the
Adam's apple.
137. Puberty and Female Voice
● In females, the larynx does not grow as big as it does in males.
● In general, a male's vocal cords are longer and more massive than
a female's. Hence, a male's voice has a lower pitch compared to
that of a female's voice
138. Characteristics
of Sound
Loudness
● Sound intensity
is perceived by
the human ear
as loudness.
The greater the
intensity, the
louder the
sound.
A high- pitched sound must be a high-frequency sound
consisting of short waves, while a low-pitched sound must
be a low-frequency sound made up of long waves.
139. Characteristics
of Sound
Quality
● Quality or timbre is
the characteristic
of sound that
distinguishes it
from another
sound of the same
pitch and intensity. The lowest frequency an instrument can produce is
called its fundamental frequency. All other frequencies
are multiples of the fundamental frequency. These are
called harmonics.
142. The Perception
of Sound
● The ear is
the organ for
hearing. It is
divided into
three parts:
outer,
middle, and
inner.
The outer ear, called the pinna or auricle, is the part of the ear at the
side of the head. The middle ear is an air-filled space containing the
eardrum and the bridge of ossicles. The inner ear contains a coiled,
fluid-filled tube called cochlea.
144. The Hearing Process in Humans
A. The pinna collects sound waves and transmits them to
the ear canal.
B. These waves then travel through the eardrum.
C. The pressure variation resulting from the compressions
and rarefactions in sound waves causes the eardrum to
vibrate.
D. The vibrations of the eardrum, in turn, cause the malleus
to vibrate.
E. The malleus strikes the incus each time it vibrates. The
incus passes the vibration to the stapes.
145. The Hearing Process in Humans
F. The vibratory motion of the stapes is transmitted to the
cochlear fluid.
G. The cochlear fluid moves in response to these vibrations.
H. The nerve endings transform these vibrations into
electrical signals and send these to the brain.
I. The brain interprets these signals as sound.
146. The Audible
Range
Generally, the ability
to hear high-
frequency sounds
deteriorates with age.
As one grows older,
one may have
difficulty hearing
high-frequency
sounds.
147. The Audible Range
● Sounds with frequencies lower than 20 Hz are called infrasounds.
Sounds with frequencies higher than 20000 Hz are called ultrasounds.
Al-Hilphy, Asaad & Altemimi, Ammar & Mehdi, Hassan & Anand, Uttpal & Delgado Pando, Gonzalo & Lakhssassi, Naoufal. (2020). Ultrasound applications in
poultry meat processing: A systematic review: Ultrasound applications in poultry meat…. Journal of Food Science. 85. 10.1111/1750-3841.15135.
148. Lowering the volume
of the stereo, talking in a
moderate voice, and not making
unnecessary noise, especially at
night, are simple but effective
ways to reduce noise pollution.
151. 7TH GRADE
OBJECTIVES
1
discuss the
uses and
importance of
light
2
investigate the
phenomena of
rectilinear
propagation of
light and its
implications in
everyday life and
optical systems
3
apply knowledge
of light properties
to real-world
scenarios, such as
optical illusions,
refraction, and
reflection
152. Theories about Light
Wave Theory
● In 1690, Dutch
physicist
Christiaan
Huygens
proposed that
light was a
wave.
x
153. Theories about Light
Corpuscular/
Particle Theory
● In 1704, English
physicist Isaac
Newton proposed
that light consists
of tiny particles
emitted by a
luminous object. x
154. Theories about Light
Electromagnetic
Theory
● Scottish physicist James
Clerk Maxwell’s equations
revealed that light is an
electromagnetic wave.
● These waves have a great
range of frequencies (or
wavelengths), in which
visible light is only a small
part. Visible light ranges from 3.94x1014 to
7.32x1014 Hz (or from 4.1×10-7 to 7.6×10-7
m).
155. Theories about Light
Quantum Theory
● German physicist Max
Planck (1858- 1947)
theorized that light was
emitted in discrete packets
of energy, called quanta.
● German- American
physicist Albert Einstein
(1879-1955) called each
quantum of energy photon.
157. Colors of Light
Visible light
● Visible light has a
by the eye,
frequency range
between 3.94×1014
and 7.32×1014 Hz
(or a wavelength
ranging from about
410 to 760 nm).
Red has the longest wavelength but has the lowest
frequency. Violet has the shortest wavelength but has
the highest frequency
Color of Light Wavelength
Red 700 nm
Orange 610 nm
Yellow 590 nm
Green 550 mn
Blue 470 mn
Violet 380 nm
158. There is a direct proportionality between
the frequency of light and its energy.
This relationship is given by the formula:
E = bf
where b is the Planck's constant = 6.63×10-
34 J·s
159. The speed of light in a vacuum has a speed
of 299,792,458 m/s or 3×108 m/s.
This speed is usually represented by a small
letter c and this value has been a standard
since 1983.
165. The Path of Light
Rectilinear Propagation of Light
Accordingly, light travels through a homogeneous medium in a
straight line because a straight line is the shortest distance
between two points. This property of light traveling in a straight
line is called the rectilinear propagation of light.
French
mathematician
Pierre de Fermat
(1601-1665) states
that the path taken
by light going from
one point to another
is the path that
requires the least
time
166.
167. An object can be seen because of the light it emits or
reflects.
An object that can generate its own light is a luminous
object.
An object that cannot generate its own light but receives
and reflects light from a luminous object is an illuminated
object.
168. The sun and the
stars are luminous
bodies,
The moon and the
planets are
illuminated bodies.
169. The Path of Light
The Intensity of Light
Illumination depends on two factors: the brightness of the
source and the distance of the surface from the source.
● Illumination is the
amount of light
falling on a unit
area of a surface. It
is represented by a
capital letter E.
● The SI unit of
illumination is the
lux (lx).
170. A given amount of light spreads over a wider area as the
area gets farther from the source.
175. The particle theory of matter states that matter consists of
many very small particles (atoms or molecules) are in constant
motion and are held together by attractive forces.
Solid Liquid Gas
176. Heat
● Heat is thermal
energy that
flows between
bodies or
regions due to
temperature
difference;
hence, heat is
considered
energy in
transit.
177. Heat flows from a body at a higher temperature to one at a
lower temperature. Heat transfer continues until the bodies
reach the same temperature or thermal equilibrium.
178. Temperature
Temperature
refers to the
degree of
"hotness" or
"coldness" of a
substance and
is measured
using a
temperature
scale. The Fahrenheit, Celsius, and Kelvin scales are used to
measure temperature.
181. If the temperature of the system is increased, the average speed of the
particles and the number of collisions also increase. Thus, at higher
temperatures, a substance has greater average molecular speed.
182. Heat is thermal energy in transit, while
temperature is a measure of the
average thermal energy.
183. Heat may be transferred by
conduction, convection, or radiation.
189. Heat Transfer: Conduction
Conduction
is the
transfer of
heat from
one
substance
to another
by direct
contact.
At the point of contact, the faster-moving particles of the warmer
substance collide with the slower-moving particles of the cooler
substance.
190. Heat Transfer: Convection
The thermal
heat
transfer by a
moving fluid
medium
such as air
or gas is
convection.
When a fluid is heated, its molecules become more energetic and move faster, causing
them to spread apart and become less dense. This lower density fluid rises, while the
cooler, denser fluid sinks, creating a flow of fluid known as a convection current.
191.
192. Heat Transfer: Radiation
Heat energy can
also travel in
empty space
without contact
between the heat
source and
heated object.
Much of the energy you receive from the sun travels by radiation. Moreover, the glowing of
hot metal in an oven indicates that the metal gives off radiation.
A room with multiple lighting is warmer than a room with just a single bulb because more hot
objects radiate heat.
195. Thermal Conductors
Thermal conductors
are materials that
allow heat to be
transferred easily.
Metals like copper, aluminum,
and silver are excellent thermal
conductors, which is why they're
commonly used in applications
where heat transfer is important,
such as cooking utensils, heat
sinks in electronics, and HVAC
systems.
196. Thermal Insulators
Thermal
insulators are
mostly used to
stop or lessen
wasted energy.
They're crucial for maintaining
temperature stability in various
applications, from keeping
buildings warm in winter to
preventing electronic devices from
overheating. Common thermal
insulators include fiberglass, foam,
mineral wool, and cellulose.
