Accounts

The Human Eye and the Colourful World

Defects Of eye

Common defects of vision include myopia (nearsightedness), hypermetropia (farsightedness), and Presbyopia.

(1) Myopia

Myopia is commonly known as nearsightedness, is a refractive error of the eye that affects the ability to see distant objects clearly.

Myopia is a condition where the eye can see nearby objects clearly but has difficulty focusing on objects that are far away. In a myopic eye, distant objects appear blurred.

A person with this defect has the far point nearer than infinity. Such a person may see clearly upto a distance of a few metres.

In a myopic eye, the image of a distant object is formed in front of the retina and not at the retina itself

Myopia often occurs when the eyeball is elongated, or the cornea is too curved.

Correction of Myopia

Wearing glasses or contact lenses with concave lenses helps diverge the incoming light rays, allowing them to focus on the retina.

(2) Hypermetropia

Hypermetropia, also known as farsightedness or long-sightedness, is a common refractive error of the eye where distant objects can be seen more clearly than close ones

It is a condition where the eye can see distant objects clearly but has difficulty focusing on nearby objects. In a hypermetropic eye, close objects appear blurred.

The near point, for the person, is farther away from the normal near point (25 cm).

In a Hypermetropia eye,image of a closeby object are focussed at a point behind the retina

Hypermetropia often occurs when the eyeball is shorter than normal, or the cornea is too flat.

Correction of Hypermetropia Wearing glasses or contact lenses with convex lenses helps converge the incoming light rays, allowing them to focus on the retina.

REFRACTION OF LIGHT THROUGH A PRISM

A prism is a transparent optical object with flat, polished surfaces that refract light. The most common type of prism is a triangular prism, which has a triangular base and rectangular sides. When light passes through a prism, it undergoes refraction, bending, and dispersion.

Process of Refraction in a Prism

(i)Incidence of Light: A beam of white light is incident on one of the prism's surfaces at an angle to the normal.

(ii)Refraction at the First Surface: As the light enters the prism, it slows down and bends towards the normal due to the change in medium from air to glass (or another transparent material). This is the first refraction.

(iii)Traveling Through the Prism: The light travels through the prism, and its path may be affected by the angles and shape of the prism.

(iv)Refraction at the Second Surface: As the light exits the prism, it speeds up and bends away from the normal, moving from the glass into the air. This is the second refraction.

(v) This angle between incident ray and emergent ray is called the angle of deviation

Dispersion of White Light by Glass Prism

When light falls on the prism it splits the incident light into band of colours. The sequence of colours observed are VIBGYOR (Violet, Indigo, Blue, Green, Yellow, Orange and Red). This band of colour is known as Spectrum. So, this splitting of incident light into different colours is known as Dispersion. This splitting is due to bending of light rays at different angles. Violet light bends most whereas red light bends least. The phenomenon of rainbow is also due to dispersion of light.

The band of these seven colours formed because of dispersion of light is known as Spectrum.

is matter around us pure class 9 notes

Pure : Pure means that there is no mixing in a substance. A pure substance is made up same kind of elements .

Example : Water, gold

Mixture : It constitute two of more substance is any proportion .

Example : Air is mixture of oxygen, nitrogen, carbon dioxide , tea

Mixture

· Homogeneous

· Heterogeneous

Homogeneous: These mixture has no visible boundaries of a separation between substance. It is in uniform composition. Example - sugar in water, salt in water

Heterogeneous: These mixture has visible boundaries of separation between substances. It is non uniform composition. Example : sand in water , chalk in water .

Solution: Solution is a homogeneous mixture of two or more substance .Example: sugar solution, salt solution

Solution has a two component.

· Solute

· Solvent

Solute : The substance that is added to the solvent to form a solution is called a Solute. For Example, Salt, when mixed in water, acts as a solute for the mixture

Solvent : The substance in which another substance is mixed is called the Solvent. For Example, Water is a solvent in which we can mix different substances such as salt or sugar.

Properties of solution ( True Solution )

The size of solute particle are smaller 10 ^-9
Solute particles cannot seen by naked eyes
Particle do not scatter a beam of light
Path of beam light not visible in solution
Stable solution
Not show the tyndall effect

C Concentration of solution

Dilute solution: Solution that contain less amount of solute is called dilute solution .

Concentrated solution: solution that contain high amount solute is called concentrated.

Saturated solution: When no more solute can be dissolved in solution at given temperature then is is called saturated solution. Saturation of solution increase when temperature increases.

Suspension : A suspension is a heterogeneous mixture in which solute particle do not dissolve but remain suspended but remain suspended. Example : muddy water, chalk in water , milk of magnesia , paints etc.
Properties of Suspension

Size of solute partical are big
Can be seen by naked eyes
Particle scatter a beam of light
Path of beam light visible in suspension
May of may not show tyndall effect
Unstable solution.

Class 9 Science Chapter 9 Force and Laws of Motion complete explanation

Force : Push of pull on an object is called force.

It is defined as the push of pull on an object with mass that causes it to change its velocity. It is a vector quantity. Example : To open or close the door .

Force and Laws of Motion complete explanation

Effect of Force

· Force can move a stationary object

· Force can stop a moving object.

· Force can change the direction of moving object.

· Force can change the speed of moving object.

Type of Force

Balanced force : if the resultant of applied force is equal to zero, than it is called balanced force .

balanced force

Unbalanced force : if the resultant of applied forces is greater than zero, than it is called unbalanced force.

F = ma

(F : force M : mass a : acceleration )

SI unit of force is newton (N)

Newton’s laws of motion

Newton studies the idea of Galileo and gave the three laws of motion

· First law of motion – Inertia

· Second law of motion – Momentum

· Third law of motion

First law of motion – Any object at rest remains in the state of rest and any object in motion will continue in motion along a straight line with uniform speed until it is compelled y an external force to change its state.

Inertia : It is the tendency of object due to which it resists any change in its state of rest or uniform motion .

· Inertia of any object measured by its mass.

· Inertia is directly proportional to the mass.

Example : When we stop cycling: This is an example of inertia of motion that each of us must have experienced at some point. When we ride a bicycle, it accelerates from rest. But, when we stop pedaling it continues for some time till it stops due to friction

Momentum: Product of mass and velocity of an object is called momentum.

It is also called the power of a moving object. It is a vector quantity.

It is denoted by “P”

P = m * v ( mv )

· Momentum increase with increase of either mass or velocity of an object.

· Vehicle running with high speed have greater momentum as compared to vehicle running with slower speed.

Small object moving with great velocity have high momentum.

Second law of motion : It state that the rate of change of momentum is directly proportional to the force applied in the direction of force .

Force α rate of change of momentum

Mass = m

Initial velocity = u

Final velocity = v

Initial momentum = mu

Final momentum = mv

F α mv-mu

____________

F α m( v-u)

____________

F α ma

F = K ma ( K = 1)

F = ma

SI unit = kg m/s²or Newton

Third law of motion : It state that if a body exerts a force on second body , the second body exert a force that is equal in magnitude and opposite in direction .

· Every action has an equal opposite reaction

· Force exerted by fist body is action and force exerted by second body is reaction.

Example : walking , jumping from boat.

Frictional Force : The force which always opposes the motion of one body over another body is called frictional force .

life process class 10 | transportation | Revision Notes on Transportation in Animals

Transportation

All living organisms need a transport system in their bodies to perform function properly . Hence the circulatory system consist of Blood , Lymph, Heart ,Arteries and veins .

Blood :

Blood is a connective tissue in humans . It transport necessary substance to cells and transport metabolic waste product away from those same cells

The Main Component of blood :

· Plasma

· Red Blood Cells

· platelets

· White Blood Cells

Plasma :

It is yellow colour fluid it transport food, CO₂waste product etc. Almost 55% of the blood is blood plasma.

life process class 10/transportation/Revision Notes on Transportation

Red Blood Cells :

It contain hemoglobin which transport oxygen from various tissues and organs. The age of RBC is 120 days . The red colour of blood due to presence of this pigment . Almost 41% of the blood is RBC

Platelets ;

These cells help in blood clotting .

White Blood Cells :

These cells fight against harmful bacteria , virus and germs .Almost 4% of the blood is white blood cells

Blood Vessels

Blood vessels are variety of pipes which carry the blood . There are three types of blood vessels in our body . arteries , capillaries , and veins .

Arteries : These carry oxygenated blood from heart to body pats except pulmonary artery . These are the thick and elastic , This is because blood flow through them at high pressure .

Capillaries : The smallest vessels which are one cell are called capillaries .The oxygenated blood from arteries enter into the capillaries in all the part of the body .

Veins : veins carry deoxygenated blood from body parts to heart except pulmonary veins. These are thin and less elastic

fundamental unit of life class 9 notes |cell || class 9 science chapter 5 notes

fundamental unit of life class 9 notes

Cell Definition :

A Cell is defined as the smallest , basic unit of the life that is responsible for all of life's process .

" Cell are structural , functional and biological unit of all living beings . They are called building blocks of the life "

Robert hooke was the first Biologist who discovered cells in 1665.

Discovery Of Cells :

Robert Hooke discovered the cell in 1665 . Robert hooke observed a piece of bottle cork under a compound microscope and noticed tiny structure that reminded him of small rooms.

Role of cells : They provide structure to the body and convert the nutrients taken form the food into energy.

fundamental unit of life

Characteristic of cells

Cell provide structure and support to the body of an organism.
Every cell has one nucleus and membrane bound organelles .
Cell store hereditary information .

Types of Organisms on the Basis of Number of Cells

All organisms are made up of cells.

Unicellular Organisms : The organisms which are made up only one cell.
Mulitcellular Organisms ; The organisms which are made up of many cells. Example - human being, animals

Types of Cells :

Cells are similar to factories with different labourers and departments that work towards a common objective , various types of cells perform different function based on cellular structure , there are two types of cells .

Prokaryotes
Eukaryotes

Prokaryotes

Eukaryotes

· Have no nucleus.

· They are single celled microorganisms.

· The size range is between .01 to .05 nano meter

· Cell division by binary fission .

· Have a true nucleus.

· They are multicelullar microorganisms.

· The size of cell range between 10- 100 nano meter.

· Plasma membrane is responsible for monitoring the transport of nutrients in and out of the cell.

· Cell division by mitosis or meiosis.

Cell Structure ;

The cell structure comprises individual components with specific function essential to carry out life process. These component include cell wall , cell membrane , cytoplasm , nucleus, and cell organelles .

Cell Membrane

Cell membrane is outer covering of a cell, is also called plasma membrane . Cell membrane support and protect the cells .It control the movement of substance in and out of the cells. It is selectively permeable in nature.

Cell Wall:

The cell wall is the most prominent part of the plant's cell structure .it is made of cellulose , hemicellulose .It protect the plasma membrane. It provide shape and support to the cells.

It is absent in animal cell. Also help in transport of various substances in and out of the cell.

Nucleus:

It sends signal to the cells to grow mature , divide and die.
The nucleus contains the hereditary material of the cell the DNA.
Nucleus is surrounded by nuclear envelop that separate the DNA from the rest of the cells.
It was discovered by Robert Brown in 1831.
It control all the metabolic activates of the cell.

Cell

Cytoplasm :

The cytoplasm is a thick clear jellly like substance present inside the cell membrane .

Most of the chemical reactions within a cell take place in this cytoplasm. It dissolves cellular wastes.

Cell Organelles:

Cell organelles are specific structure present inside a particular type of cell that perform specific function .There are numerous cell organelles .

Nucleolus :

The nucleolus is the site of ribosome synthesis , also it is involved in controlling cellular activities and cellular reproduction . Nucleolus contain RNA.

Chromosomes :

Chromosome play a crucial role in determining the sex of an individual. Each human cells contain 23 pairs of chromosome .Chromosome found only eukaryotic animal cells.

Endoplasmic Reticulum:

Endoplasmic reticulum is involved in the transportation of substances throughout the cells. It play a primary role in the metabolism of carbohydrates Synthes of lipids, steroids and proteins . It also help in membrane propagation. It is absent in Prokaryotic cell.

Endoplasmic reticulum are two types

(i) Smooth reticulum

(ii) Rough reticulum

Golgi Apparatus :

Golgi bodies are the cell's post office as it is involved in the transportation of material within the cell. It was discovered by Camilo Golgi. It is absent in Prokaryotic cell. It involved in the formation of the lysosomes.

Mitochondria :

The power house of the cell. It is called so because it produce ATP. The cell energy currency. Rod shaped organelles .Mitochondria have two membrane covering.

class 9 gravitation notes | Universal law of Gravitation | gravitation|| whats gravity | gravitation class 9 notes

Gravitation Class 9 Notes

Gravitational Force : Every object in this universe attract every other object with a certain force .
The force with which two object attract each other is called gravitational force .

Gravitational force is a non contact force .

> The strength of the gravitational attraction between two object depends on two factors

How big the object are
How far apart they are

Universal law of Gravitation

Given by newton also known as newton's law of gravitation , Everybody in the universe attract every other body with a force which is directly proportional to the product of their masses and inversely proportional to the squire of the distance between them

GM₁M₂

_{F = __________}

R²

where G is the universal gravitation constant.

Value of G = 6.673*10-11Nm2Kg-2

Gravitational force

Importance of Universal law of Gravitation

It bind us to the earth
It is responsible for the motion of the moon around the earth
It is responsible for the motion of planets around the sun
Gravitational force of moon causes tides in the sea on earth .

class 9 gravitation notes

Free Fall: The falling of a body or object from height towards the earth under gravitational force of earth ( with no other force acting on it ) and such a body is called freely falling body.

Acceleration due to Gravity (g) :

The uniform acceleration produced in a freely falling body due to gravitational force of the earth is known as acceleration due to gravity.

Value of acceleration due to gravity is 9.8 m/s²

> g does not depends on the mass of the falling object of smaller mass .

Calculation of acceleration due to gravity ( g) -

F= mass * acceleration

F= ma = GM₁M₂

_{_____________________________}

R²

^{acceleration came due to the gravity of the earth}

g = GM

_________

R²

G g = 6.67x10^-11 x 6 x 10²⁴

_______________________ = 9.8 m/s²

(6.4 x 10⁶)²

The three equation of motion

Equation of motion

Motion due to gravity

· v= u +at

^·S = ut + ½ at²

· v²- u² = 2as

· v= u +gt

^·S = ut + ½ gt²

· v²- u² = 2gs

> When a body is falling vertically downwards its velocity is increasing. So the acceleration due to gravity is taken as positive

. g = + 9.8 m/s²

^>When a body is thrown vertically upwards its velocity is decreasing . So the acceleration due to gravity is taken as negative

g = - 9.8 m/s²

> If an object is just drop or fall from a height then u = 0

Difference between Mass and Weight

Mass

Weight

· Actual content present in a body

· Mass is always constant

· Mass is never zero or negative

· SI unit = Kg

· It is the force exert by the body on earth.

· Weight is variable ( change from place to place )

· Weight = mass * acceleration

· Weight can be zero.

· SI unit = N ( newton)

Gravity on moon is 1/6 less than the earth

gravity on earth

Gravity on moon = __________________