Why Do We Fall Ill Notes | Class 9 CBSE Science Notes

Important Notes of Why Do  We Fall ill

Health: It is a state of complete physical mental and social well being, not merely an absence of disease. Good Health constitutes a healthy body with healthy mind as well as healthy attitude.
 It renders an individual happy and cheerful
Makes living a joyful experience.
 Increases efficiency for all the activities of life

Factors that affect the Health of an individual
 a)physical environment
b)Social environment
c)Mental state of an individual
 d)Economic Conditions

 The community and the environment in which an individual lives directly affect the health of an individual.Community health care provisions involve Clean and safe drinking water Efficient system for disposal of garbage, sewage and rainwater Medical care facilities Educating the people to make them understand the ways of keeping good health

 Disease is a improper functioning of body organs due to one or the other reason The word disease literally means absence of comfort or not being at ease In the diseased state, either form or function of one or more part of the body gets altered.

Changes in form or functions appear as symptoms and sigsn of the disease.
Symptoms of the disease are changes and the feeling that make an individual uncomfortable Different diseases manifest same symptoms like fever,headache,cough and loose motions.

Signs of the disease are changes that indicate a specific cause A symptom can be defined as one of the characters of a disease. Meanwhile, sign is the definite indication of a specific disease.

Physicians diagnose diseases on the basis of the specific signs and symptoms and confirm on the basis of laboratory tests

On the basis of duration of occurrence, the diseases are classified into two categories
ACUTE Disease:
 It lasts for very short period of time for e.g common cold
 Patient recovers completely after the cure
There is no loss of weight or feeling of tiredness
afterward
There is short duration loss of work and
efficiency


 Chronic Disease:
It persist for long time even as much as life time e.g elephantiasis.
Patient does not recover completely
There is often loss of weight of feeling of
tiredness
There is a prolonged loss of work and efficiency


Causes of Diseases : Most of the diseases have many causes, rather than one single
cause, like unclean water, nourishment, genetic differences, genetic abnormalities e.g.
Based on the causes diseases are of two types: Non-Infectious Diseases and Infectious
Diseases.

Diseases are caused due to
a)infection by microorganisms like bacteria,virus fungi, protozoa, and worms
b).Malnutrition i.e. deficiency of one or more nutrients
c).Contaminated water and air
d).Malfunctioning of different body organs
e).Genetic disorder

Immediate cause of Disease:
The agent that causes the disease is called immediate cause e.g. if a person gets jaundice, the immediate cause is virus infection

Contributory causes are factors that lend support to immediate cause to be able to cause the disease
Contaminated water is the source of infection.
He suffers from lack of resistance
He lacks resistance because he does not get proper nourishment


Infectious Diseases: Caused by infectious agents.
Infectious disease causing organism are transmitted from a sick person to healthy person by direct contant, air , water, and carriers and vectors

Group of organisms and diseases caused by them.

The signs and symptoms of the disease depend on the tissue or organs where microorganism enter and attack

• Symptoms appear due to activation of the body's immune system in response to infection.
• Activated immune system sends white blod cells to the affected tissues to fight the germs
• It causes inflammation visible in the form of rashes swelling and pain in the infected area
• Rise in body temperature may also occur. 

There are two approaches for the treatment of infectious disease
a)to reduce the harmful effects of the disease
b) To kill the casual organism of disease

Principles of Treatment:
1. Antibiotics- many bacteria make a cell wall to protect themselves, the antibiotic (Penicillin) blocks the bacterial process that builds cell wall and blocks the biochemical pathways. Antibiotics do not work against viral infections. Antiviral medicine is harder than making Antibacterial medicine because Virus has only few biochemical mechanisms of their own. Other medicines bring down fever, reduce pain or loose motions. We can take bed rest to conserve energy.

Viruses do not have cellular organisation
They enter our cells and use our cellular machinery for their life processes
As they have few biochemical mechanisms of their own it is difficult to make anti viral medicine

Principles of Prevention :
Following three limitation are normally confronted while
treating an infectious disease:
 Once someone has disease, their body functions are damaged and may never
recover completely.
 Treatment will take time, which means that someone suffering from a disease is
likely to be bedridden for some time even if we can give proper treatment.
 The person suffering from an infectious disease can serve as the source from where
the infection may spread to other people.

General ways of preventing infectious disease :
 Air-borne – We can prevent exposure by providing living condition that are not
overcrowded.
 Water-borne – prevent by providing safe drinking water. This is done by treating the
water to kill any microbial contamination.
 Vector-borne – We can provide clean environment, which would not allow mosquito
breeding.

Immunity: Even in cells there is repair mechanism called” Immunity”. Immune cells
manage to kill off the infectious agents. Smallpox disease is eliminated by developing
memory cells for particular infection by mimics the microbes, called” Vaccine”. The basis of
Immunization- if you had smallpox once, there was no chance of suffering from it again.
Proper nutrition is essential to maintain body immunity. There are vaccines against tetanus,
diphtheria, whooping cough, measles, polio and many other diseases.

Immunisation can be active or passive
Active immunisation:When the body produces anti bodies to fight against infection for which vaccination is done

Passive Immunisation:When readymade anti bodies are directly injected to provide protection

 

Class 9 CBSE Sound Chapter Notes

Important Notes of Science Class 9 CBSE Sound

Production of Sound
Sound is produced due to the vibration of objects. Vibration is the rapid to and fro motion of an object. Vibrating objects are the source of all sounds Irregular, chaotic vibrations produce noise Regular, controlled vibration can produce music All sound is a combination of pure frequencies A stretched rubber band when plucked vibrates and produces sound.

Propagation of Sound
When an object vibrates, the particles around the medium vibrate. The particle in contact with the
vibrating object is first displaced from its equilibrium position
The disturbance produced by the vibrating body travels through the medium but the particles do not
move forward themselves.

A wave is a disturbance which moves through a medium by the vibration of the particles of the
medium. So sound is considered as a wave.Sound waves Require medium for transmission.Sound
waves are called mechanical waves. When a vibrating object moves forward, it pushes and
compresses the air in front of it forming a region of high pressure called compression (C). When the
vibrating object moves backward, it forms a region of low pressure called rarefaction (R).

A vibrating object producing a series of compressions (C) and rarefaction (R)
In these waves the particles move back and forth parallel to the direction of propagation of the
disturbance. Such waves are called longitudinal waves.








Compressions are the regions of high pressure and density where the particles are crowded and
are represented by the upper portion of the curve called crest.
Rarefactions are the regions of low pressure and density where the particles are spread out and
are represented by the lower portion of the curve called trough

Sound is a Mechanical Wave:
Sound requiers medium for its propagation it can travel through solid, liquid and gas but not vaccum. The waves which require a material medium for their propagation are called mechanical waves.

Sound is Longitudnal Wave

The wave in which the particles of the medium oscillate along the direction of propagation of the wave is called a longitudinal wave

Transverse wave
The wave in which the particles of the medium oscillate in a direction perpendicular to the direction of propagation of the wave is called a transverse wave.Light waves are transverse waves.They do not require medium for their propagation.Light can travel through vaccum.


 Pulse: A wave of  short duration which is confined to a small portion of a medium at any given time is known as a pulse.


 Characteristics of a sound wave

Frequency of sound waveThe number of oscillations per unit time is called the frequency of the sound wave.
It is represented by the symbol ٧ (Greek letter nu). Its SI unit is hertz (Hz)

The pitch of a sound depends upon the frequency, higher the frequecy higher will be the pitch and vice versa.

Time Period:Time taken to complete one oscillation

Time period= 1/f

Amplitude of the Sound: The maximum displacement of particles of the medium from their mean positions during the propagation of a wave is known as amplitude of the wave.The amplitude of sound wave is the height of the crest or tough.It is represented by the letter A.
The SI unit is the same as that of density or pressure.

Velocity:The distance travelled by a wave in one second is called wave velocity.It depends upon the nature of the medium through which it passes.

v=frequency X Wavelength


Audible Frequency: The human ears can hear only those waves whose freqnecy lies between 20 Hz and 20,000HZ.

Infrasonic Waves:The waves having freqnecy less than 20 Hz are infrasonic


Ultrasonic Waves:The waves having frequency more than 20.000 Hz are ultrasonic waves

Reflection of Sound
Sound gets reflected at the surface of a solid or liquid and follows the laws of reflection.
i) The angle of incidence is equal to the angle of reflection.
ii) The incident ray, the reflected ray and normal at the point of incidence all lie in the
same plane.

 Echo
If we shout or clap near a reflecting surface like tall building or a mountain, we hear the
same sound again. This sound which we hear is called echo. It is caused due to the reflection
of sound.
To hear an echo clearly, the time interval between the original sound and the echo
must be at least 0.1 s.
Since the speed of sound in air is 344 m/s, the distance travelled by sound in 0.I s = 344
m/s x 0.1 s = 34.4 m
So to hear an echo clearly, the minimum distance of the reflecting surface should be
half this distance that is 17.2 m.



Reverberation

Echoes may be heard more than once due to repeated or multiple reflections of sound
from several reflecting surfaces. This causes persistence of sound called reverberation.

In big halls or auditoriums to reduce reverberation, the roofs and walls are covered by
sound absorbing materials like compressed fibre boards, rough plaster or draperies.















Uses Of Multiple Reflection Of Sound
 
i)Megaphones, horns, musical instruments like trumpets, etc. are deigned to send sound by
multiple reflection in a particular direction without spreading in all directions.

ii) Doctors listen to sounds from the human body through a stethoscope. The sound of
heartbeat reaches the doctor’s ears by multiple reflection.

iii) Generally the ceilings of cinema halls and auditoriums are curved so that sound after
multiple reflection reaches all parts of the hall.


Sometimes a curved sound board is placed behind the stage so that sound after multiple
reflection spreads evenly across the hall.

Speed of sound in Different Medium
Sound travels with different speeds in different mediu.The speed of sound also depends u pon the temperature of the medium.Sound travels faster in solids than in air.The speed of sound in solids is much more than the speed of sound in liquids or gases.
Average speed of sound at room temperature is 332 m/s

Application of Ultrasound
They are used to establish ship to ship communication.
They are used to find the depth of a sea.
They are used to diagnose the disease in a human body
They are used to kill bacteria in liquids.
They are used for welding plastics

SONAR
SONAR stands for Sound Navigation and Ranging.It is based on the principle of the reflection of sound wave.The ultrasonic waves from the transmitter of SONAR are sent towards the bottom of the sea whose depth is to be measured.These waves are reflected back from the bottom of the seas and are received by the receiver of the SONAR the transmitter and the receiver are suitably placed on the ship.The time taken by the ultrasonic waves to go from the ship to the bottom of the sea and then  back to the ship is recorded
Time taken by the waves to go from the ship to the bottom of the sea is =t/2.If V is the velocity of wave, the the required distance S is given by.
s= v(t/2)


Human Ear
The ear mainly consists of three basic parts the outer ear, the  middle ear, the the inner ear.Each part of the ear serves a specific purpose in the task of the detecting and interpreting sound.The outer ear serves to collect and channel sound to the middle ear.The middle ear serves to transform the energy of a sound wave into the internal vibrations of the bone structure and ultimately transform these vibrations into a compressional waves in the inner ear.The inner ear serves to transform the energy of a compressional wave with the inner ear fluid into nerve impulses which can be transmitted to the brain.