14.1
DESCRIBING
WAVES
Presented by:
MR. RYAN C. CABRERA
Bachelor of Science in Physics
Post Baccalaureate in Teacher Education
Master in Educational Management
PARTS, CHARACTERISTICS and PROPERTIES OF A WAVE
▪ Crest
– highest point of a wave.
▪ Trough
– lowest point of a wave.
▪ Amplitude
– height of the crest or trough.
– height of the wave.
▪ Wavelength ( λ )
– distance between two successive crests or troughs.
– is represented by greek letter lambda (λ ).
▪ Period ( T )
– number of seconds for one vibration.
– time that elapses between passing crests or troughs.
– in equation, T = λ / V or T = 1 / f
▪ Frequency ( f )
– number of vibrations per second and measured in Hz (hertz).
– is the number of crests (∩) or troughs (U) that pass by per unit time.
– it is equal to the inverse of the period.
– in equation, f = 1 / T
▪ Wave Speed ( V )
– rate at which the crests or troughs move forward.
– in equation, V = λ / T and V = λ f
PULSE WAVE VS. PERIODIC WAVE
Pulse wave
– single wave
Periodic Wave – repetition of pulse wave
SAME WAVELENGTH BUT DIFFERENT AMPLITUDE
SAME WAVELENGTH BUT DIFFERENT AMPLITUDE (Answer)
Crest to Crest
Crest to Crest
Crest to Crest
SAME WAVELENGTH BUT DIFFERENT AMPLITUDE
SAME WAVELENGTH BUT DIFFERENT AMPLITUDE (Answer)
λ
λ
SAME AMPLITUDE BUT DIFFERENT FREQUENCY
SAME AMPLITUDE BUT DIFFERENT FREQUENCY (Answer)
SAME AMPLITUDE BUT DIFFERENT FREQUENCY
SAME AMPLITUDE BUT DIFFERENT FREQUENCY (Answer)
A = 6 cm
A = 6 cm
LESS
frequency
MORE
frequency
LOW ENERGY WAVE VS. HIGH ENERGY WAVE
λ
Less frequency
λ
High frequency
LOW ENERGY WAVE VS. HIGH ENERGY WAVE
HIGHER
Amplitude
LOWER
Amplitude
14.2
WAVE SPEED,
FREQUENCY AND
WAVELENGTH
Presented by:
MR. RYAN C. CABRERA
Bachelor of Science in Physics
Post Baccalaureate in Teacher Education
Master in Educational Management
SYMBOL DESCRIPTION
T
Period
f
Frequency
FORMULA and UNIT
1
T=
f
s (second)
Hz (Hertz), c/s (cycles per second) , 1/s
v
1
f =
f =

T
v
Wave Speed m/s (meters per second)
v=
λ
Wavelength
m (meter)

v = f •
T
 = v •T
v
=
f
PROBLEM SOLVING
WAVE SPEED
FREQUECNY
AND WAVELENGTH
Problem # 1
A student observes some
ripples in a ripple tank. She
notes that 20 waves
occupy a distance of
4.5 cm. What is their
wavelength?
0.23 cm
Solution:
Problem # 1
A student observes some
ripples in a ripple tank. She
notes that 20 waves
occupy a distance of
4.5 cm. What is their
wavelength?
Solution:
distance
λ=
# of waves
4.5 cm
λ=
20 waves
𝛌 = 𝟎. 𝟐𝟑 𝐜𝐦
0.23 cm
Solution:
Problem # 2
Calculate the speed of
sound in air if a sound of
frequency 180 Hz has a
wavelength of 1.833 m.
329.94 m/s
Solution:
Problem # 2
Calculate the speed of
sound in air if a sound of
frequency 180 Hz has a
wavelength of 1.833 m.
329.94 m/s
V=λ∙f
V = 1.833 m 180 Hz
180
𝑠
V = 1.833 m
𝐕 = 𝟑𝟐𝟗. 𝟗𝟒
𝐦
𝐬
Solution:
Problem # 3
Sound has a speed of
1500 m/s in water. Calculate
the wavelength of sound
waves of frequency 420 Hz
in water.
3.57 m
Solution:
Problem # 3
Sound has a speed of
1500 m/s in water. Calculate
the wavelength of sound
waves of frequency 420 Hz
in water.
3.57 m
λ=
λ=
λ=
V
f
m
1500
s
420 Hz
m
1500 s
420
s
𝛌 = 𝟑. 𝟓𝟕 𝐦
Solution:
Problem # 4 A
Red light of wavelength
6.50 x 10−7 meters travels
through air, where
its
speed is 3.0 x 10 8 m/s.
a. What is its frequency?
4.62 x 10 14 Hz
Problem # 4 A
Red light of wavelength
6.50 x 10−7 meters travels
through air, where
its
speed is 3.0 x 10 8 m/s.
a. What is its frequency?
4.62 x 10 14 Hz
Solution:
f=
V
λ
f=
m
8
3 x 10 s
6.5 x 10 −7 m
𝐟 = 𝟒. 𝟔𝟐 𝐱
𝟏𝟒
𝟏𝟎 𝐇𝐳
Problem # 4 B
Red light of wavelength
6.50 x 10−7 meters travels
through air, where its speed
is 3.0 x 10 8 m/s.
b. What will its wavelength
become in glass, where its
speed is 2.1 x 108 m/s?
4.55 x 10 −7 m
Solution:
Problem # 4 B
Red light of wavelength
6.50 x 10−7 meters travels
through air, where its speed
is 3.0 x 10 8 m/s.
b. What will its wavelength
become in glass, where its
speed is 2.1 x 108 m/s?
4.55 x 10 −7 m
Solution:
λ=
V
f
λ=
m
8
2.1 x 10
s
4.62 x 10 14 Hz
λ=
m
8
2.1 x 10 s
4.62 x 10 14
s
𝛌 = 𝟒. 𝟓𝟓 𝒙 𝟏𝟎−𝟕 𝐦
Problem # 5
Ultrasound
waves
are
sometimes used to clean small
items of jewellery, which are
immersed in water and
subjected to ultrasound. What
is the wavelength of ultrasound
waves of frequency 45 kHz in
water? Give your answer in cm.
(Speed of ultrasound in water =
1500 m/s.)
3.33 cm
Solution:
Problem # 5
Ultrasound
waves
are
sometimes used to clean small
items of jewellery, which are
immersed in water and
subjected to ultrasound. What
is the wavelength of ultrasound
waves of frequency 45 kHz in
water? Give your answer in cm.
(Speed of ultrasound in water =
1500 m/s.)
3.33 cm
Solution:
λ=
λ=
λ=
V
f
m
1500
s
45 000 Hz
cm
150 000 s
45 000
s
𝛌 = 𝟑. 𝟑𝟑 𝐜𝐦
14.3
EXPLAINING
WAVE
PHENOMENA
Presented by:
MR. RYAN C. CABRERA
Bachelor of Science in Physics
Post Baccalaureate in Teacher Education
Master in Educational Management
PROPERTIES OF WAVES
A.
B.
C.
D.
REFLECTION
REFRACTION
DIFFRACTION
INTERFERENCE
REFLECTION
Bouncing off waves
on a surface.
TYPES OF REFLECTION
A.
SPECULAR REFLECTION
B.
DIFFUSED REFLECTION
A. SPECULAR
REFLECTION
θi = θr (angle of incidence is
EQUAL to angle of reflection)
Incident rays strikes a
SMOOTH SURFACE wherein
the reflected rays goes to
only ONE DIRECTION.
B. DIFFUSED
REFLECTION
θi ≠ θr (angle of incidence is
NOT EQUAL to angle of
reflection)
Incident rays strikes a
ROUGH SURFACE wherein
the reflected rays goes to
DIFFERENT DIRECTIONS.
REFRACTION
BENDING OF WAVES
as it pass through from
one medium into
another medium.
CHANGING DIRECTION
because of a
change in speed.
DIFFRACTION
Bending of waves around the
edges or corners of a barrier.
small openings – produce
great diffractions
large openings – produce
less diffractions
SMALL OPENING
VS.
LARGE OPENING
INTERFERENCE
MEETING OF TWO OR
MORE WAVES that
produces different points of
intersection.
Two types
a. Constructive interference
b. Destructive Interference
CONSTRUCTIVE INTERFERENCE
Occurs when the crest or
trough of the first wave MEET
the crest or trough of the
second wave.
DESTRUCTIVE INTERFERENCE
Occurs when the crest or
trough of the first wave DO NOT
MEET the crest or trough of the
second wave.
CONSTRUCTIVE INTERFERENCE
DESTRUCTIVE INTERFERENCE
CONSTRUCTIVE INTERFERENCE
DESTRUCTIVE INTERFERENCE