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ACOUSTIC(SOUND):-
→Classification of Sound
On basis of frequency sound are classified in three ways:-
→Infra – sound:- The sound having frequency less than 20Hz are infra-sound. They are
not audible sound
→Audible Sound:- The sound having frequency less than 20Hz to 20KHz are called
audible sound.
→Ultra – Sound:- The sound having frequency more than 20KHz are called ultrasound. They are also not audible.
❖ Classification of Audible Sound
→Musical Sound:- The sound which produces pleasant effect on ear is called musical
sound. The musical sound wave form are regular in shape having definite periodicity
and don’t undergo sudden change in amplitude.
Ex :- Sound emitted by musical instrument.
→Noise:- The sound which produces jarring effect on ear and is unpleasant to ear is
called noise. The noise waveform is irregular in shape, not having definite
periodically and undergo sudden change in amplitude.
Ex :- Sound produced from traffic.
CHARACTERISTICS OF MUSICAL SOUND
→Musical Sound have three characteristics through which two sound emitted either
from same source or different can be distinguished.
1) Loudness:- It is that characteristics of musical sound which differentiate two sound
coming from same source but at different level.
→ It depends on amplitude of sound.
loudness α (Amplitude)2
∴ loudness is also known as intensity of sound.
→ It also depends on distance from source
loudness α
1
(distance)
2
→ It depends on surface of vibrating body.
→ It depends on density of medium.
more density more loudness.
→Pitch:- The characteristics of musical sound which distinguish two sound emitted
from same source having same loudness on basis of frequency.
Low Pitch High Pitch
Bass Treble
Woofer Shrill
Men Women
→Timber:- It is also known as quality of sound two sounds having same loudness,
same pitch but from different instrument are distinguished by timber.
→Waveform are different.
Violin Piano
- ECHO & REVERBERATION
ECHO:-
→When any sound produced from source falls on any other object and gets bounce
back, this bouncing back of sound after striking any surface is called reflection of
sound.
→If sound reaches to listener after reflection before 0.1 sec, then listener can’t
listen/hear sound again. But if the sound reaches to listener after reflection after 0.1
sec, then the listener listen/hear sound again.
→Thus this phenomena of repetition of sound caused by reflection of sound is called
echo.
REVERBERATION:
-
→The sound produced in a hall suffers successive reflection from wall, floor, ceiling
and other reflecting materials in hall.
→Hence in addition to sound produced by source in hall, the listener hear series of
sound waves. Due to this series of sound waves, sound persist in room even after the
source have stopped to emit sound.
→Thus this phenomena of persistence of sound due to multiple no of reflection even
after the source have stopped to emit sound is called reverberation
ECHO & REVERBERATION ECHO:-
→When any sound produced from source falls on any other object and gets bounce
back, this bouncing back of sound after striking any surface is called reflection of
sound.
→If sound reaches to listener after reflection before 0.1 sec, then listener can’t
listen/hear sound again. But if the sound reaches to listener after reflection after 0.1
sec, then the listener listen/hear sound again.
→Thus this phenomena of repetition of sound caused by reflection of sound is called
echo.
REVERBERATION:-
→The sound produced in a hall suffers successive reflection from wall, floor, ceiling
and other reflecting materials in hall.
→Hence in addition to sound produced by source in hall, the listener hear series of
sound waves. Due to this series of sound waves, sound persist in room even after the
source have stopped to emit sound.
→Thus this phenomena of persistence of sound due to multiple no of reflection even
after the source have stopped to emit sound is called reverberation.
TYPES OF OSCILLATIONS/VIBRATION
Free Vibration/Oscillations :-
→It takes place where no external resistance force acts on
the particle.
→Since no resistance force acts on the particle hence
particle will oscillates/vibrate for infinite time.
→Amplitude will remain constant through out the
oscillations/vibration.
→Frequency of vibration/oscillation of particle under free
vibration/oscillation is called natural frequency and
every object/particle has its own natural frequency.
→A body capable of oscillating/vibration is said to be executing free
oscillation/vibration if its vibrates with its own natural frequency without
help of any external periodic force.
DAMPED OSCILLATION :-
→ When a particle executing
SHM oscillates with decreasing
amplitude with time, then the
oscillation is called damped
oscillation.
FORCED OSCILLATION
→Every body have tendency to vibrate/oscillate
with natural frequency. But in forced
vibration. The body will vibrate oscillate with
frequency of external periodic force.
→Thus when a body oscillate with the help of
external periodic force with a frequency
different than its natural frequency such
oscillation is called forced oscillation.
→In forced oscillation amplitude of oscillation
is small.
RESONANCE :-
→When the driving force frequency ie external periodic force frequency equals to
natural frequency of particle then amplitude of oscillation become maximum this
phenomena is called Resonance.
CHARACTERISTICS OF WAVE MOTION
→In wave motion, the disturbance travels through the
medium due to repeated periodic oscillations of the
particles about their mean position.
→The energy is transferred from one location to
another without actual transfer of particle.
→The velocity with which the wave travels is different
from the velocity with which particle oscillate.
→In the given medium, the wave velocity remains
constant, while the particle velocity changes
continuously about its mean position.
→In wave motion each particle receives disturbance
latter than its preceding particle.
TYPES OF WAVE
❖ Transverse Wave :-
1) The particles of the medium vibrates
about their mean position in direction
perpendicular to wave motion.
2) The wave travels in form of crest and
trough. A crest and a trough to gather
form a wave.
3) At crest displacement of particle is
maximum and at trough displacement
of particle is maximum (negative).
4) They can be produced only in solids
or at surface of liquids. They can’t be
produced inside liquid or gases.
5) Ex :- Wave produced in string.
❖ Longitudinal Wave :-
1) The particles of the medium vibrates
about their mean position along the
direction of wave motion.
2) The wave travels in form of
compression and rare fraction. A
compression and rare fraction together
forms a wave.
3) At compression the velocity of particle
is maximum and at rare fraction
velocity is minimum.
4) They can be produced in all the three
medium solid, liquid and gases.
5) Ex :- Sound Waves.
OPTICS
→Light:- It is a form of energy which provides
us sense of vision and without light we can’t
see any object present on the earth.
→Ray of light:- Light travels in a straight line
path known as ray of light.
→Beam of light:- Group of ray of light are
collectively known as beam of light.
REFLECTION OF LIGHT
→When the ray of light travelling in a medium
strikes a smooth polished surface its gets
bounce back in the same medium. This
phenomena is called Reflection of light
→The incident ray, reflected ray and
normal at the point of incidence
lies on the same plane.
→The angle of incidence (Angle
between incident ray & normal)
and the angle of reflection (Angle
between reflected ray and normal)
are always equal.
∠i = ∠r
SPHERICAL MIRROR & ITS IMPORTANT TERMS
→Those mirrors or reflecting surfaces which are a part of a hollow sphere are called
Spherical mirror.
→These mirror are of two types:-
a) Concave Mirror
b) Convex Mirror
→Concave Mirror:- It is a part of hollow sphere such that its outer surface (ie bulging surface) is silvered while its inner surface (ie depressed surface) is reflecting surface.
→Convex Mirror:- It is a part of hollow sphere having
inner surface (depressed surface) is silvered surface and
outer surface (buldging surface) is reflective surface.
ITS IMPORTANT TERMS
→Center of Curvature:- The center of a
hollow sphere of which spherical
mirror forms a part is called center
of curvature. It is represented by (C).
→Radius of Curvature:- Radius of a
hollow sphere of which spherical
mirror forms a part is called radius
of curvature. It is represented by ‘R’.
→Pole:- The mid point of spherical mirror
is called pole. It is the vertex of mirror.
It is represented by (P).
→Principle Axis:-The line joining pole and
center of curvature is called principle
axis.
→Principle Focus:- The point on the
principle axis where the ray of light
parallel to principle axis meets or
appears to meet after reflection.
→Focal length:- The distance between
pole and principle focus is called focal
length.
→Aperature:- The effecting diameter of
light reflecting area.
.
