SNELL’S LAW

SNELL’S LAW

According to Snell’s law
"The ratio of the sine of the angle of incidence to the sine of the angle of refraction is always constant. "
Mathematically,
Sine <i/sine <r = constant or sin< i/sine< r = m
where m = Refractive index of the material of medium.
TOTAL INTERNAL REFLECTION
When light rays enter from one medium to the other, they are refracted. If we increase the angle of     incidence, angle of refraction will also increase. At certain angle of incidence light rays are reflected     back to the first medium instead of refraction. This condition or phenomenon is called Total Internal     Reflection.
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CRITICAL ANGLE
The angle of incidence at which the angle of refraction will become 90o is called Critical Angle. If angle     of incidence further increased then instead of refraction, reflection will take place.
DEFECTS OF VISION Write down the defects of the vision.
There are four common defects of vision:     1. SHORT SIGHTEDNESS OR MYOPIA     2. LONG SIGHTEDNESS OR HYPER METROPIA     3. ASTIGMATISM    4. PRESBYOPIA
SHORT SIGHTEDNESS OR MYOPIA
SYMPTOMS
In Myopia, a person can not see distant objects clearly, but he can see clearly the objects near to him.
REASON
The reason for Myopia is either the focal length of lens of eye is too short or the eyeball is very much     elongated.
WHAT HAPPENS IN MYOPIA
In Myopia, light rays from a distant object are focused in front of the Retina.
CORRECTION OF DEFECT
This defect can be corrected by using a concave lens of suitable focal length

KINETIC MOLECULAR THEORY OF MATTER

KINETIC MOLECULAR THEORY OF MATTER
According to kinetic theory of matter:
Matter is made of very small particles called MOLECULES. These molecules are in a state of motion. They possess Kinetic Energy. Molecular motion may be translational , rotational or vibrational. These molecules attract each other. As the temperature of a substance is increased , its molecular speed is also increased and vice versa. If a substance is compressed , The K.E of its molecules increases and its temperature rises For latest information , free computer courses and high impact notes visit : www.citycollegiate.com
BROWNIAN MOTION
A famous scientist ROBERT BROWN observed that molecules of a substance are moved in ZIG ZAG path. Their motion is random. They collide with each other and move in a new direction after collision in ZIG ZAG fashion. This type of motion present in the molecules of matter is called "Brownian motion".
Brownian motion
ELASTICITY
The property of solid by virtue of which a solid body recovers its original shape after the removal of an applied force is called "ELASTICITY".
ELASTIC LIMIT
If applied force on a solid is gradually increased, a state is reached after which the material will not return to it original shape even after the removal of applied force. This limit is called "ELASTIC LIMIT". After elastic limit, material is permanently deformed. Different substances have different elastic limit.
STRESS
When a body is deformed, the internal force came into play per unit area to restore it to its original state is called "STRESS" OR "Stress is an opposing force expressed per unit area which resists any change in shape."
Stress is equal to the force per unit area. Mathematically:
or
Stress produces when a body is made to change in length, volume or Shape by the application of an external force

STATES OF EQUILIBRIUM

States of equilibrium
There are three states of equilibrium:
Stable equilibrium    Unstable equilibrium    Neutral equilibrium
Stable equilibrium
When the center of gravity of a body lies below point of suspension or support, the body is said to be in    STABLE EQUILIBRIUM. For example a book lying on a table is in stable equilibrium.
Explanation
A book lying on a horizontal surface is an example of stable equilibrium. If the book is lifted from one edge    and then allowed to fall, it will come back to its original position.    Other examples of stable equilibrium are bodies lying on the floor such as chair, table etc.
Reason of stability
When the book is lifted its center of gravity is raised . The line of action of weight passes through the    base of the book. A torque due to weight of the book brings it back to the original position.
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Unstable equilibrium
When the center of gravity of a body lies above the point of suspension or support, the body is said to    be in unstable equilibrium
Example
pencil standing on its point or a stick in vertically standing position.
Explanation:    If thin rod standing vertically is slightly disturbed from its position it will not come back to its original    position. This type of equilibrium is called unstable equilibrium, other example of unstable equilibrium are    vertically standing cylinder and funnel etc.
Reason of instability
when the rod is slightly disturbed its center of gravity is lowered . The line of action of its weight lies    outside the base of rod. The torque due to weight of the rod toppled it down.
Neutral equilibrium
When the center of gravity of a body lies at the point of suspension or support, the body is said to be in    neutral equilibrium. Example: rolling ball.
Explanation
If a ball is pushed slightly to roll, it will neither come back to its original nor it will roll forward rather it will    remain at rest. This type of equilibrium is called NEUTRAL EQUILIBRIUM.
Reason of neutral equilibrium
If the ball is rolled, its center of gravity is neither raised nor lowered. This means that its center of gravity    is at the same height as before.

ADVANTAGES AND DISADVANTAGES OF FRICTION - METHODS OF REDUCING FRICTION

ADVANTAGES AND DISADVANTAGES OF FRICTION - METHODS OF REDUCING FRICTION

ADVANTAGES OF FRICTIONFriction plays a vital role in our daily life. Without friction we are handicap. 1. It is becomes difficult to walk on a slippery road due to low friction. When we move on ice, it     becomes difficult to walk due to low friction of ice. 2. We can not fix nail in the wood or wall if there is no friction. It is friction which holds the nail. 3. A horse can not pull a cart unless friction furnishes him a secure Foothold. DISADVANTAGES OF FRICTION Despite the fact that the friction is very important in our daily life, it also has some disadvantages like: 1. The main disadvantage of friction is that it produces heat in various parts of machines. In this way     some useful energy is wasted as heat energy. 2. Due to friction we have to exert more power in machines. 3. It opposes the motion. 4. Due to friction, noise is also produced in machines. 5. Due to friction, engines of automobiles consume more fuel which is a money loss. METHODS OF REDUCING FRICTIONThere are a number of methods to reduce friction in which some are discussed here. USE OF LUBRICANTS:The parts of machines which are moving over one another must be properly lubricated by using oils and lubricants of suitable viscosity. USE OF GREASE:Proper greasing between the sliding parts of machine reduces the friction. USE OF BALL BEARING:In machines where possible, sliding friction can be replaced by rolling friction by using ball bearings. DESIGN MODIFICATION:Friction can be reduced by changing the design of fast moving objects. The front of vehicles and airplanes made oblong to minimize friction.

FORCE & MOTION

"Force is an agent which changes or tends to change the state  of rest or of uniform motion of a body."
In the light of Newton's 2nd law of motion Force may be defined as :
"Force acting on a body is equal to the product of the mass and acceleration produced in the body."
i.e.
F = ma
Force can accelerate or decelerate a body.  Force is a vector quantity.
UNITS OF FORCE
(i) NEWTON (N) in S.I system    (ii) DYNE in C.G.S system    (iii) POUND (Lb) in BRITISH ENGINEERING SYSTEM (F.P.S)
NEWTON
Newton is the unit of force and can be defined as:
"The amount of force that produces an acceleration of 1 m/s2 in a body of mass 1-kg is equal to 1 NEWTON."
1 N = 1 kg x 1m/s2
[ N = kg m/s2]
NEWTON 'S FIRST LAW OF MOTION
STATEMENT:    Newton 's first law of motion states that:
"Every body remains at rest or continues to move with uniform velocity in straight line unless an unbalanced force acts upon it".
EXPLANATION
First law of motion consists of two parts:
PART NO 1:
The first part states that a body at rest remains at rest unless an unbalanced force acts upon it.    This part is in accordance with our common experience for example, a book lying on a table remains at    rest unless it is lifted or pushed by an external force.
PART NO 2 :
Second part states that a body in motion remains in motion with uniform velocity unless an unbalance    force acts upon it. This part is not self-evident because a ball pushed once does not continue its motion    forever. A little consideration however, shows that there is an opposing force like ground friction and air    friction acting in this case. These frictional forces are responsible to stop the ball. If we eliminate these    opposing forces, a body in motion will continue its motion forever.
INERTIA
"Tendency of a body by virtue of which the body at rest or moving with uniform velocity retains its state is called INERTIA."
OR
"Property of a body by which a body resists a force, applied to it to change its state of rest or of uniform velocity is called INERTIA."
INERTIA of a body is directly related to its mass. Heavy bodies have greater inertia while lighter bodies    have little inertia.
LAW OF INERTIA AND THE FIRST LAW OF MOTION
Every body in the universe opposes the force which tends to change its state of rest or of uniform    motion. This property INERTIA is a direct consequence of FIRST LAW OF MOTION. As heavy bodies due    to greater INERTIA requires forces of large magnitude and bodies of small masses require small forces.    By the above explanation of INERTIA we conclude that the state of rest or motion does not change by its    self unless an external force acts upon it, which is according to the FIRST LAW OF MOTION.    Thus the FIRST LAW OF MOTION is also called LAW OF INERTIA.

EQUATIONS OF MOTION EQUATIONS OF MOTION

FIRST EQUATION OF MOTION Vf = Vi + at
Consider a body initial moving with velocity "Vi". After certain interval of time "t", its velocity becomes "Vf". Now
Change in velocity = Vf - Vi  OR DV =Vf – Vi
	Due to change in velocity, an acceleration "a" is produced in the body. Acceleration is given by
	a = DV/t
	Putting the value of "DV"
	a = (Vf – Vi)/t at = Vf – Vi at + Vi =VfOR
	SECOND EQUATION OF MOTION OR S = Vit + 1/2at2
	Consider a car moving on a straight road with an initial velocity equal to ‘Vi’. After an interval of time ‘t’ its velocity becomes ‘Vf’. Now first we will determine the average velocity of body.
	Average velocity = (Initial velocity + final velocity)/2 OR Vav = (Vi + Vf)/2
	but Vf = Vi + at
	Putting the value of Vf
	Vav = (Vi + Vi + at)/2 Vav = (2Vi + at)/2    Vav = 2Vi/2 + at/2   Vav = Vi + at/2                            Vav = Vi + 1/2at.......................................(i)
	we know that
	S = Vav x t
	Putting the value of ‘Vav’
	S = [Vi + 1/2at] t
	THIRD EQUATION OF MOTION OR 2aS = Vf2 – Vi2
	Initial velocity, final velocity, acceleration, and distance are related in third equation of motion.
	Consider a body moving initially with velocity ‘Vi’. After certain interval of time its velocity becomes ‘Vf’. Due to change in velocity, acceleration ‘a’ is produced in the body. Let the body travels a distance of ‘s’ meters.  According to first equation of motion:
	Vf = Vi + at      OR Vf – Vi = atOR                          (Vf – Vi)/a = t....................(i)
	Average velocity of body is given by:
	Vav = (Initial velocity + Final velocity)/2                               Vav = (Vi + Vf)/2.................. (ii)
	we know that :
	S = Vav x t.................. (ii)
	Putting the value of Vav and t from equation (i) and (ii) in equation (iii)
	S = { (Vf + Vi)/2} { (Vf – Vi)/a} 2aS = (Vf + Vi)(Vf – Vi)
	According to [ (a+b)(a-b)=a2-b2]

KINEMATICS

KINEMATICS
"Kinematics is the branch of Physics in which we discuss bodies at rest or motion without the reference of external agent that causes motion or rest."  OR "The branch of physics which deals with the description of motion of objects without reference to the force or agent causing motion in it, is called Kinematics."
REST
	"If a body does not change its position with respect to its surroundings then the body is said to be in a state of rest."
	MOTION
	"If a body continuously changes its position with respect to its surrounding than it is said to be in a state of motion."
	TYPES OF MOTION
	Motion of objects can be divided into three categories.
	(i) TRANSLATIONAL MOTION (ii) ROTATIONAL MOTION (iii) VIBRATIONAL MOTION
	TRANSLATIONAL MOTION
	"Motion of a body in which every particle of the body is being displaced by the same amount is called Translational Motion".
	EXAMPLE:  (i) Motion of a person on a road. (ii) Motion of a car or truck on a road.
	ROTATIONAL MOTION
	"Type of motion in which a body rotates around a fixed point or axis is called Rotational Motion."
	EXAMPLE:  (i) Motion of wheel (ii) Motion of the blades of a fan
	VIBRATIONAL MOTION
	"Type of motion in which a body or particle moves to and fro about a fixed point or mean position is called Vibratory Motion."
	EXAMPLE: (i) Motion of simple pendulum (ii) Motion of the wires of guitar (iii) Motion of swing
	DISPLACEMENT
	"Distance between two points in a particular direction is called Displacement." OR Displacement may also be defined as "the minimum distance between two points in a particular direction."
	It is a vector quantity and is always directed from the initial point to the terminal point. It is denoted by "d".
	SPEED
	"Distance covered by a moving body in one second is called its Speed". OR "Distance covered by a body in unit time is called Speed".
	Speed is a scalar quantity.
	FORMULA
	Speed = Distance traveled/Time taken  OR v = S/t
	UNIT
	Unit of speed in S.I system is "m/sec".
	VELOCITY
	"Distance covered by a body in a particular direction in one second is called Velocity". OR "Displacement of a body in unit time is called Velocity". OR "Change of position of a body per second in a particular direction is called Velocity."
	FORMULA
	velocity = displacement/time
	UNIT
	In S.I system unit of velocity is meter/second. It is a vector quantity.
	ACCELERATION
	"The rate of change of velocity of a body is called Acceleration." OR "Change in velocity of a body in unit time is called its acceleration."
	It is denoted by "a". It is a vector quantity. If a body moves with uniform velocity or constant velocity then its acceleration will be zero. UNIT: m/sec2.
	FORMULA
	Acceleration = change in velocity/time OR a = DV/t

SCALARS & VECTORS

SCALAR QUANTITIES
Physical quantities which can completely be specified by a number (magnitude) having an appropriate unit are known as "SCALAR QUANTITIES".
Scalar quantities do not need direction for their description. Scalar quantities are comparable only when they have the same physical dimensions. Two or more than two scalar quantities measured in the same system of units are equal if they have the same magnitude and sign. Scalar quantities are denoted by letters in ordinary type. Scalar quantities are added, subtracted, multiplied or divided by the simple rules of algebra.
	EXAMPLES
	Work, energy, electric flux, volume, refractive index, time, speed, electric potential, potential difference, viscosity, density, power, mass, distance, temperature, electric charge, electric flux etc.
	VECTORS QUANTITIES
	Physical quantities having both magnitude and direction with appropriate unit are known as "VECTOR QUANTITIES".
	We can't specify a vector quantity without mention of deirection.  vector quantities are expressed by using bold letters with arrow sign such as: vector quantities can not be added, subtracted, multiplied or divided by the simple rules of algebra. vector quantities added, subtracted, multiplied or divided by the rules of trigonometry and geometry.
	EXAMPLES
	Velocity, electric field intensity, acceleration, force, momentum, torque, displacement, electric current, weight, angular momentum etc.
	REPRESENTATION OF VECTORS
	On paper vector quantities are represented by a straight line with arrow head pointing the direction of vector or terminal point of vector.
	A vector quantity is first transformed into a suitable scale and then a line is drawn with the help of the
	scale choosen in the given direction.

MEASUREMENT

.
MEASUREMENT
Meter
Meter is the unit of length in S.I. System.   Meter is defined as "The distance between the two marks on a Platinum-Iridium bar kept at 0OC in the   International Bureau of Weight and Measures in Paris."   One meter = 100 cm   One meter = 1000 mm
Kilogram
Kilogram is the unit of mass in S.I. System.   "Kilogram is defined as the mass of a platinum cylinder placed in the International Bureau of Weight and   Measures in Paris."   One kilogram = 1000gram
Second
Second is the unit of time in S.I. System.   A second is defined in terms of the time period of Cs-133 atoms.  i.e." one second is equal to 9,192,631,770 periods of vibrations of Cs-133 atoms."   60 seconds = one minute   3600 seconds = one hour
Least Count
Minimum measurement that can be made by a measuring device is known as " LEAST COUNT'.
Least count (vernier callipers) = minimum measurement on main scale / total number of divisions on                                                                                                              vernier scale
.
Least count (screw gauge) = minimum measurement on main scale / total number of divisions on                                                                                                   circular scale
Smaller is the magnitude of least count of a measuring instrument, more precise the measuring   instrument is.   A measuring instrument can not measure any thing whose dimensions are less than the magnitude of   least count.   Least Count of Vernier Callipers = 0.01 cm   Least Count of Micrometer Screw gauge = 0.001 cm
Zero Error
It is a defect in a measuring device (Vernier Callipers & Screw Gauge).   When jaws of a Vernier Callipers or Screw Gauge are closed, zero of main scale must coincides with the   zero of vernier scale or circular scale in case of screw gauge.   If they do not coincide then it is said that a zero error is present in the instrument.
Types Of Zero Error
Zero error may be positive or negative.
A positive zero error in the instrument shows a larger measurement than the actual measurement.  In order to get exact measurement, positive zero error is subtracted from the total reading.
.
A negative zero error in the instrument shows a smaller measurement than the actual measurement.   In order to get exact measurement, negative zero error is added to the total reading.
Pitch
"Perpendicular distance between two consecutive threads of the screw gauge or spherometer is called PITCH."
Pitch = Distance traveled on main scale / total number of rotations
Error
An error is defined as "The difference between the measured value and actual value."
If two persons use the same instrument for measurement for finding the same measurement, it is not   essential that they may get the same results. There may arises a difference between their   measurements. This difference is referred to as an "ERROR".
Types Of Error
Errors can be divided into three categories:   (1) Personal Error   (2) Systematic Error   (3) Random Error
Personal Error
An error comes into play because of faulty procedure adopted by by the observer is called "PERSONAL   ERROR".   Personal error comes into existence due to making an error in reading a scale. It is due to faulty   procedure adopted by the person making measurement.
Systematic Error
The type of error arises due to defect in the measuring device is known as "SYSTEMATIC ERROR".   Generally it is called "ZERO ERROR". it may be positive or negative error. Systematic error can be   removed by correcting measurement device.
Random Error
The error produced due to sudden change in experimental conditions is called "RANDOM ERROR".   For example:   Sudden change in temperature, change in humidity, fluctuation in potential difference (voltage).   It is an accidental error and is beyond the control of the person making measurement.

Organic Chemistry Introduction

What Organic Chemistry Is and What Organic Chemists 

Organic chemistry is more than simply the study of carbon or the study of chemicals in living organisms. Take a look at what organic chemistry is, why it is important, and what organic chemists do.

What Is Organic Chemistry?
Organic chemistry is the study of carbon and the study of the chemistry of life. Since not all carbon reactions are organic, another way to look at organic chemistry would be to consider it the study of molecules containing the carbon-hydrogen (C-H) bond and their reactions.

Why Is Organic Chemistry Important?
Organic chemistry is important because it is the study of life and all of the chemical reactions related to life. Several careers apply an understanding of organic chemistry, such as doctors, veterinarians, dentists, pharmacologists, chemical engineers, and chemists. Organic chemistry plays a part in the development of common household chemicals, foods, plastics, drugs, fuels... really most of the chemicals part of daily life.

What Does an Organic Chemist Do?

An organic chemist is a chemist with a college degree in chemistry. Typically this would be a doctorate or master's degree in organic chemistry, though a bachelor's degree in chemistry may be sufficient for some entry level positions. Organic chemists usually conduct research and development in a laboratory setting. Projects that would use organic chemists would include development of a better painkilling drug, formulating a shampoo that would result in silkier hair, making a stain resistant carpet, or finding a non-toxic insect repellent.