Bridge course Science Part 1 Activity Sheet 01
Bridge course 2021 -2022
Science and Technology Part 1
Class 10th Activity
Sheet 01
Lets understand :
Sound waves , Sound velocity , sound reflection, Human ear ,audible
, infra sound and ultra sound.
Refrence: Class 9th unit no.12th
Study Sound.
Expected Skills:
1) Explain the
importance of different concepts of sound in everyday life and solve different
problems.
2) Prepare a detailed outline of the sonar technique and
explain it
3) Explaining the function of human ear through diagram in contest of sound .
Let's
keep in mind: Sound is a form of energy which creates the
sensation of hearing in our ears. This energy is in the form of waves. A medium
is necessary for the propagation of sound waves. Sound waves give rise to a
chain of compression (place of higher density) and rarefaction (place of lower
density) in the medium. The particles of the medium oscillate about their
central or mean positions, in a direction parallel to the propagation of the
wave. Such waves are called longitudinal waves.
On the other hand, in the waves created by dropping a stone in still
water, the particles of water oscillate up and down. These oscillations are
perpendicular to the direction of propagation of the wave, such waves are
called transverse waves.
v
Velocity of sound:
The
distance covered by a point on the wave (for example the point of highest
density or lowest density) in unit time is the velocity of the sound wave.
Ø
Velocity=Wave length X Time period
V = 
ʎ
v
Limits
of hearing , infra sound and ultra sound :
The limits
of hearing of the human ear are 20 Hz to 20,000 Hz. These sounds are called
audible sounds.
>Human ear cannot
hear sounds of frequencies lower than 20 Hz and higher than
20,000 Hz (20 kHz).
> Sound with frequency smaller than 20 Hz is called infra
sound.
>Sound with frequency greater than 20 Hz is called ultra
sound.
v
Refection
of sound :
Ø
Echo:
An echo is
the repetition of the original sound because of reflection by some surface.
Ø
Reverberation:
Sound waves
get reflected from the walls and roof of a room multiple times. This causes a
single sound to be heard not once but continously. This is called
reverberation.
Ø
SONAR:
>SONAR is
the short form for Sound Navigation and Ranging.
>It is
used to determine the direction, distance and speed of an underwater object
with the help of ultrasonic sound waves.
>SONAR
has a transmitter and a receiver, which are fitted on ships or boats.
>The
transmitter produces and transmits ultrasonic sound waves.
>These
waves travel through water, strike underwater objects and get reflected by
them. >The reflected waves are received by the receiver on the ship.
>The
receiver converts the ultrasonic sound into electrical signals and these
signals
are properly interpreted. The time difference
between transmission and reception
is noted.
>This
time and the velocity of sound in water give the distance from the ship, of the
object which reflects the waves.
>SONAR
is used to determine the depth of the sea. SONAR is also used to search
underwater hills, valleys, submarines,
icebergs, sunken ships etc.
Human
Ear:
>The ear
is an important organ of the human body.
> We
hear sounds because of our ear.
>When
sound waves fall on the eardrum, it vibrates.
>These
vibrations are converted into electrical signals which travel to the brain
through
nerves.
>The ear can be divided into three parts:
1. Outer ear 2. Middle ear 3. Inner ear.
Outer ear or Pinna :The outer ear collects the sound waves and passes
them through a tube to a cavity in the middle ear. Its peculiar funnel like
shape helps to collect and pass sounds into the middle ear.
Middle
ear : There is a thin membrane
in the cavity of the middle ear called the eardrum. When a compression in a
sound wave reaches the eardrum, the pressure outside it increases and it gets
pushed inwards. The opposite happens when a rarefaction reaches there. The
pressure outside decreases and the
membrane gets pulled outwards. Thus, sound waves cause vibrations of the
membrane.
Inner ear: The auditory nerve connects the inner ear to the brain. The inner ear
has a structure resembling the shell of a snail. It is called the cochlea. The
cochlea receives the vibrations coming from the membrane and converts them into
electrical signals which are sent to the brain through the nerve. The brain
analyses these signals.
Lets
Practice:
1) What is
the difference between a sound wave and a water waves?
2) Write
any two use of sound reflection which happen in your surrounding . .
3) You must have seen
the interior walls inside the function hall. What steps are taken to reduce the
echo there?
4) Write any three
uses of ultrasound .
Link for more information: https://play.google.com/store/apps/details?id=in.gov.diksha.app&referrer=utm_source%3Dmobile%26utm_c ampaign%3Dshare_app
https://www.youtube.com/c/Biosciencewala