Grade:
8
Quarter/Semester: FIRST
I.
OBJECTIVES
Content Standard
Performance Standard
Learning Competencies
Knowledge
Skills
Attitude
II.
III.
CONTENT
LEARNING
RESOURCES
References
Subject:
Week No:
4
SCIENCE
Day
5
The learners demonstrate an understanding of the propagation
of sound through solid, liquid, and gas.
Investigate the effect of temperature to speed of sound through
fair testing.
S8FE-Ie-25
Differentiate reflection and refraction of sound.
Observe how longitudinal waves reflect and refract.
Appreciate the importance of reflection and refraction of sound in
our day to day activities.
REFLECTION AND REFRACTION OF SOUND
Science 8 Learner’s Materials pp. 85-90
Science 8 Teachers Guide p. 55
Other Learning Resources
IV.
PROCEDURES
A. Preparatory Activities  Prayer and checking of attendance.
 Let the student display their assignment task in a table. Choose
3 students to present their assignment to the class.
B. Motivation
Ask students to cite examples of amazing contribution of sound
to other fields such as in health, wellness and the arts particularly
in music industry.
Ans.: ultrasound image, live concert or music, use to map the
sea floor and determine the depth of the ocean or sea, use to
detect distance
C. Activity
D. Analysis
Want to know more about these amazing sound treats?
Students will perform activity 6, “Reflecting and Refracting
sound”.
In this activity the students will be able to observe how
longitudinal waves reflect and refract.
Let the students answer the following guide questions.
Q32. What happens to the compressions or rarefactions when
they hit the wall or a fixed end?
Ans.: The compressions or rarefactions bounce off after
hitting the wall.
Q33. Are the compressions found on the same location in the
slinky before and after hitting the wall?
Ans.: No they are not found on the same positions.
Q34. What happens to sound waves when they hit a fixed end or
the wall?
Ans.: Sound will also bounce off when it strikes a fixed end
or the wall.
Q35. What happens to the frequency of the longitudinal waves
as the waves move from the large coil slinky to the small
coil slinky?
E. Abstraction
Ans.: The frequency of the wave increases.
Q36. What would be an observable change in sound when the
frequency changes?
Ans.: Increase in frequency of the sound is manifested as
change in pitch.
Q37. What happens to the amplitude of the longitudinal waves as
the waves move from the large coil slinky to the small coil
slinky?
Ans.: Amplitude increases.
Q38. What happens to sound when the amplitude of the sound
changes?
Ans.: Louder sound is observe.
Q39. What happens to the speed of the longitudinal waves as
the waves move from the large coil slinky to the small coil
slinky?
Ans.: Faster wave.
Introduce the properties of sound, reflection and refraction of
sound.
Reflection of sound is usually described as the turning back of a
wave as it hits a barrier. Echo is an example of a reflected sound.
Reverberation on the other hand refers to the multiple reflections
or echoes in a certain place. Echo sounding is another
application of sound reflection. This is used by scientists to map
the sea floor and determine the depth of the ocean or sea.
Refraction of sound is described as the change in speed of sound
when it encounters a medium of different density. As what you
had learn, sound travels faster in hotter media. This change in
speed of sound during refraction is manifested as sort of
“bending” of waves. When sound propagate in air, where the
temperature changes with altitude, sound bends towards the
hotter region, thus refraction happens.
F. Application
G. Practical
Applications of
Concepts and Skills
in Daily Living
When sounds propagates in air, where the temperature changes
with altitude, sound bends towards the hotter region, thus
refraction happens. The refraction is due to the different
refractive indices of air because of the difference in temperature.
At day time, the air near Earth’s surface is cooler than the air
above. Sound would move from the cooler region (Earth surface)
towards the hotter air above. Thus sound waves will be refracted
to the sky. At nighttime, the air near the Earth’s surface is heated
by the heat emitted by the sun during nighttime. This makes
sound move from the cooler air above towards the hotter air near
the earth’s surface. Thus, sound waves are refracted to the
Earth’s surface.
Why do designers use curtains, cloth or rough materials to cover
the walls and ceiling of a theater or movie house? What property
is being applied?
Ans.: To lessen the echoes and reverberations which are not
pleasing to the ears during a play or a movie.
Reflection of sound.
Why open field concerts are usually held during nighttime?
Ans.: Open field concert at night gives a chance for everyone to
see and enjoy the live show because there is no work and no
school. Aside from that, sound is heard well in far areas and gives
a clearer and more audible music to enjoy during nighttime as
sound waves are refracted from the stage towards the audience
due to refraction.
Name different practical applications of reflection and refraction
of sounds in our day to day activities.
1. Hearing aid – a device used by the people who are having a
difficulty in hearing. Sound waves are uniformly reflected in a
slimmer area so as to direct the sound to the ear.
2. Sound Boards – Curved surfaces which are used in auditorium
to spread the waves uniformly throughout the hall to avoid
echoes and reverberation. It helps in improving the quality of
sounds.
3. Sonar devices – used to measure the distance and speed of
underwater objects through sound.
H. Generalization
I. Evaluat
J. ion
V.
VI.
K. Additional activities
for application or
remediation
(assignment)
REMARKS
REFLECTION
No. of learners who
earned 80% in the
evaluation
No. of learners who
continue to require
remediation
Did the remedial lesson
work? No. of learners
who caught up the
lesson
4. Stethoscope – the sound of the patient’s heartbeat reaches the
doctor’s ear by multiple reflections of sound using this device.
5. Horns, megaphones or loudhailers – are designed to send
sound waves in particular direction without spreading in all
directions.
6. Parking sensor – The sensors measure the time taken to
reflect each sound pulse back to the receiver. The device will
alert the driver of the possibility of collision by audio means.
Sound is a form of energy.
Reflection and refraction are the properties of sound.
An echo is a reflected sound while reverberation is a multiple
reflection of sound.
Sound refraction occurs in uneven winds or when sound is
travelling through air of uneven temperature.
Answer the questions briefly.
1. Differentiate reflection and refraction of sound.
Ans.: Reflection of sound is described as the turning back of
sound wave as it hits a barrier while refraction of sound is
described as the change in speed of sound when it
encounters a medium of different temperature. Thus sound
bends.
2. Compare echo and reverberation.
Ans.: Echo is an example of a reflected sound while
reverberation refers to the multiple reflections of sound.
3. How to lessen the echo and reverberation in a movie house?
Ans.: To lessen the echo and reverberation in a movie house
put sound boards, curtains, cloth to spread the waves
uniformly throughout the hall to avoid echoes and
reverberation.
4. Why are open field concerts held during nighttime?
Ans.: Sound is heard well in far areas and gives a clearer and
more audible music to enjoy during nighttime as sound waves
are refracted from the stage towards the audience due to
refraction.
Assignment:
1. What are the properties and characteristics of light?
2. Define refraction of light.
3. Name the members of the electromagnetic spectrum.
No. of learners who
require remediation
Which of my teaching
strategies worked well?
Why did these work?
What difficulties did I
encounter which
principal and supervisor
can help or solve?
What innovation or
localized did I
use/discover which I
wish to share?
Prepared by:
ADELINE FE D. DIMAANO
Teacher III
Balugo National High School
Valencia District
ATTACHMENT
(Attachment for Activity 6, Reflecting and refracting of sound)
Name: ______________________________
School:______________________________
Yr. and Sec.: ______________
Date: ____________________
Activity 6
Reflecting and Refracting of Sound
Objective:
At the end of the activity, you will be able to observe how longitudinal waves reflect and
refract.
Materials:
metal slinky (large coil)
metal slinky (small coil)
Procedure:
Sound Reflection
1. Connect the fixed end to a wall or post. Make or create longitudinal waves by pushing and
pulling the movable end part.
2. Observe the longitudinal waves as the waves hit the wall or post. Record your observations.
3. Note the positions of the compressions before they reach the post. Note also the locations or
positions of the compressions after hitting the wall of the post.
4. Do this for 3 trials.
Q32. What happens to the compressions or rarefactions when they hit the wall or a fixed
end?
______________________________________________________________________
Q33. Are the compressions found on the same location in the slinky before and after hitting
the wall?
______________________________________________________________________
Q34. What happens to sound waves when they hit a fixed end or the wall?
______________________________________________________________________
Sound Refraction
1. Connect the fixed end of the metal slinky (small coil) to a wall or post. Then connect another
slinky (large coil) to the other end of the small coil. Make or create longitudinal waves by
pushing and pulling the movable end of the metal slinky (large coil).
2. Observe the longitudinal waves as the waves move from the large coil-metal slinky to the small
coil metal slinky. Record your observations.
3. Observe the frequency, amplitude, and speed of the longitudinal waves as the waves move
from the large coil metal slinky to the small coil metal slinky.
4. Do this for 3 trials.
Q35. What happens to the frequency of the longitudinal waves as the waves move from
the large coil slinky to the small coil slinky?
______________________________________________________________________
Q36. What would be an observable change in sound when the frequency changes?
______________________________________________________________________
Q37. What happens to the amplitude of the longitudinal waves as the waves move from t
the large coil slinky to the small coil slinky?
______________________________________________________________________
Q38. What happens to sound when the amplitude of the sound changes?
______________________________________________________________________
Q39. What happens to the speed of the longitudinal waves as the waves move from the
large coil slinky to the small coil slinky?
______________________________________________________________________