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.
For latest information ,
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

REFLECTION OF LIGHT DEFINITIONS

REFLECTION OF LIGHT
When light rays traveling is a medium reaches the boundary of other medium, they turn back to the     first medium. This phenomenon of turning back of light into the same medium after striking the boundary     of other medium is called Reflection of Light.
LAWS OF REFLECTION
1. The angle of incident is equal to the angle of reflection i.e. <i = <r     2. The incident ray, the reflected ray and the normal lie on the same plane.
REGULAR REFLECTION
When a beam pass of parallel light rays is incident on a smooth and plane surface, the reflected rays will     also be parallel. This type of reflection is called Regular Reflection.
IRREGULAR REFLECTION
When a beam of parallel light rays is scattered in all directions. Therefore the parallel rays incident on     the surface will reflect in different directions. This type of reflection is called "Irregular or Diffuse     Reflection".
CENTER OF CURVATURE
Center of curvature of a lens or mirror is defined as the center of the sphere of which the less or mirror     is a part. C = Center of curvature.
RADIUS OF CURVATURE
Radius of curvature is the radius of sphere of which the lens or mirror is a part.
PC = Radius of curvature OR PC = R
POLE
For latest information , free computer courses and high impact notes
The middle or center point of a lens or a mirror is called "Pole" P = Pole.
PRINCIPLE AXIS
The straight line joining the center of curvature to the pole is called Principle Axis. .
PRINCIPLE FOCUS
When a narrow beam of light, parallel to the principle axis and closed to it, is incident on the surface of     a mirror or lens, the beam reflected or refracted is converged at a fixed point on the axis. This point is     called Principle Axis.     F = principle focus.
FOCAL LENGTH
The distance between the pole of a lens or mirror to the principal focus is called Focal Length (PF) of     lens or mirror. Focal length is always equal to half of the radius of curvature of lens or mirror. f = R/2.
Write down the characteristics of image formed by a plane mirror
1. Image formed by plane mirror is laterally inverted. This means that right side of the object appears on     the left side.     2. Size of image formed by plane mirror is the same as that of size of object.     3. The image formed by plane mirror is virtual because it can not be obtained on the screen.     4. The image is as far behind the mirror as the object is in front of the mirror. Fig.
DEFINE SPHERICAL MIRROR AND IT'S TWO TYPES
SPHERICAL MIRROR
Mirror obtained from a spherical surface is known as Spherical Mirror. A spherical mirror is considered as     a section of hollow sphere.
TYPES OF SPHERICAL MIRRORS
There are two types of spherical mirrors.     1. Concave mirror.     2. Convex mirror.
CONCAVE MIRROR
If the inner side of the surface of a spherical mirror is polished to reflect light, the mirror is called a     Concave Mirror. Concave mirror converges parallel beam of light.
CONVEX MIRROR
If the outer side of the surface of a spherical mirror is polished to reflect light the mirror is called a     Convex Mirror. Convex mirror diverges parallel beam light.
MAGNIFICATION
Magnification of a mirror or lens is defined as the ratio of the size of image to the size of object.
M = height of image/height of object M = hi/ho  or M = q/P
REFRACTIVE INDEX
Refractive index is defined as the ratio of sine of the angle of incidence of the sine of the angle of     refraction. FORMULA :
m= sine< i/ sine< r
note :Refractive index depends upon the nature of material.     It has no unit.
ANGLE OF DEVIATION
The angle at which the light ray is refracted (bend) in a prism is called angle of deviation. It is denoted     by < D. Minimum value of angle of deviation is called angle of minimum deviation. It is denoted by     <Dm.

TORQUE - CENTER OF GRAVITY

TORQUE - CENTER OF GRAVITY

Torque
The torque or moment of force can be define as
“ The tendency of a force to produce rotation in a body about an axis is called torque or moment of force."
The turning effect of a force depends upon two factors:    The magnitude of force (F)    Moment arm (r)    The torque about any axis is given by the product of force and moment arm
Torque = force x moment arm OR
Positive torque:    If a body rotates about its axis in anti clockwise direction, then the torque is taken positive .
Negative torque:    If the body rotates in the clockwise direction, then the torque is taken as negative .
For latest information , free computer courses and high impact notes visit :
Center of gravity
The center of a body is that point in the body through which the resultant forces due to the earth’s    attraction posses and through which the whole weight of the body always acts.    OR    Center of gravity of a body is a point where total weight of the body is concentrated.    Every body posses a center of gravity and this is irrespective of the body. Its is not necessary that the    center of gravity should be within the body, but it may also be situated in space out side the body.    Example: center of gravity of a ring is at the center, which is in the space.    Center of gravity of different objects:    Rectangle    Center of gravity of a rectangular is at the point of intersection of its diagonals    Circle    Center of gravity of a circle is at its center.    Square    Center of gravity of square is at the point of intersection of its diagonals.    Regular bar    The center of gravity of a regular bar is at its geometrical center.     Triangle    The center of gravity of a triangle is at the point of intersection of its medians.     Cylinder    The center of gravity of a cylinder is at the axis of cylinder.

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.
For latest information , free computer courses and high impact notes visit :
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.

Momentum- Law of conservation of Momentum

MOMENTUM
Quantity of motion of a body is referred to as "MOMENTUM".
Definition
Momentum of a moving body defined as :
"the product of mass and velocity of a body is called MOMENTUM."
Mathematically
Momentum = mass x velocity
It is a vector quantity. Momentum is always directed in the direction of velocity.    The unit of momentum is in S.I system kg .m/s or NS.    Momentum depends upon mass and velocity of body.
LAW OF CONSERVATION OF MOMENTUM.
The law of conservation of momentum states that:
"when some bodies constituting an isolated system act upon one another, the total momentum of the system remains constant." OR "the total momentum of an isolated system of interacting bodies remains constant." OR "Total momentum of an isolated system before collision is always equal to total momentum after collision."
Consider an isolated system of two bodies 'A' and 'B' as shown. The masses of bodies are ma and mb and
MATHEMATICAL REPRESENTATION
Consider two bodies of mass m1 and m2 moving initially with velocities u1 and u2.
Total momentum before collision = m1u1 + m2u2
Let after collision their velocities become v1 and v2.
Total momentum after collision = m1v1 + m2v2
According to the law of conservation of momentum
m1u1 + m2u2 = m1v1 + m2v2

DIFFERENCE BETWEEN MASS AND WEIGHT

Mass		Weight
(1) The quantity of matter in a body is          called its mass.		(1) Weight is the force by which the earth          attracts a body towards its center.
(2) Mass is a scalar quantity.		(2) Weight is a vector quantity and is always          directed towards the center of the earth.
(3) Mass of a body is always constant          every where in the universe.		(3) Weight of a body vary place to place and          become zero on the center of earth and far          away from the surface of earth.
(4) Mass of a moving body is m=F/a.		(4) Weight of a body is W = mg.
(5) Mass can be determine by an          ordinary balance.		(5) Weight of a body is measured by spring          balance.
(6) Unit of mass in S.I system is          KILOGRAM ( kg).		(6) Unit of weight in S.I system is NEWTON (N).
FRICTION
When a body slides over the surface of another body, an opposing force is set up between them to resist    the motion. The force which opposes the motion is called friction OR Force of Friction.
Force of friction tends to decelerate a body and always acts in the opposite direction of motion.
CATEGORIES OF FRICTION    (1) Contact friction    (2) Fluid friction
LIMITING FRICTION
When an external force is applied against the force of friction, the force of friction also increases by the    same amount. Therefore, It adjusts itself in such a way that it is equal and opposite to the external    force. It has a maximum value just before the motion starts. So friction is a self-adjusting force. The    maximum force of friction that stops the body from moving is called LIMITING FRICTION.    It is denoted by Fs.    LIMITING FRICTION is directly proportional to the surface reaction.
Limiting friction Fs is:
Where R = normal reaction  but R = W and R = mg
Where = constant known as coefficient of friction.
COEFFICIENT OF FRICTION
Coefficient of friction is the ratio of LIMITING FRICTION to the NORMAL REACTION.
Coefficient of friction is constant for a given pair of surfaces but different for different pairs
Unit of :    Since it is a ratio of two similar quantities, therefore it has no unit as shown.
ROLLING FRICTION		www.citycollegiate.com
When a body rolls over a surface, the force of friction is called ROLLING FRICTION. When a sphere rolls    over a surface it experiences an opposing force called ROLLING FRICTION.    Rolling friction is much less than the sliding friction because in case of rolling contact area of two surfaces    is very small as compared to sliding.

NEWTON'S 2ND LAW OF MOTION

When an unbalanced force acts upon a body, it is accelerated in the direction of force. The magnitude of acceleration is directly proportional to the applied force and is inversely proportional to the mass of body.
MATHEMATICALLY
Combining (i) and (ii)
....
a = k (F)(1/m) here constant k=1
a= (1)(F)(1/m) Or
SECOND STATEMENT
With the help of above equation 2nd law of motion can be expressed as:
THE NET FORCE ACTING ON A BODY IS EQUAL TO THE PRODUCT OF THE MASS OF BODY AND THE ACCELERATION PRODUCED IN IT.
NEWTON'S 3RD LAW OF MOTION
STATEMENT:
"To every action there is a reaction equal in magnitude but opposite in direction"
OR
"When a body exerts a force on another body, the second body also exerts a force on the first body of same magnitude but in the opposite direction"
FACTION = -FREACTION
Force exerted by one body is called ACTION and the force exerted by the second body is called    REACTION.
EXAMPLES:    (1) Motion of rocket: fuel burns rapidly, exerts force in downward direction and rocket moves upward        as a reaction.    (2) Book lying on a table: weight of the book on the surface is action and the force exerted by the          surface (R) is the reaction.                         R = -W    (3) Walking on a street    (4) Motion of helicopter