LONG SIGHTEDNESS OR HYPER METROPIA

SYMPTOMS
In HYPER METROPIA, a person can not see objects clearly which are near to him, but he can see clearly     distant objects
REASON
The reason for HYPER METROPIA is that either the focal length of the lens of eye is too long or the     eyeball is too short.
WHAT HAPPENS IN HYPER METROPIA
In HYPER METROPIA, light rays from a near object are focused behind the Retina.
CORRECTION OF DEFECT
This defect can be corrected by using a convex lens of suitable focal length
POWER OF LENS
Power of lens is defined as the reciprocal of the focal length of the lens in meters.
FORMULA:
Power = 1/f(in meter)
Unit of power of lens is Dioptre.
DIOPTRE
Dioptre is defined as the power of lens whose focal length is one meter
if f =1 meter then the power of the lens = 1 dioptre.

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

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
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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.

SIMPLE PENDULUM

SIMPLE PENDULUM
	simple pendulum consists of a heavy mass particle suspended by a light, flexible and in-extensible string.
	MOTION OF THE BOB OF SIMPLE PENDULUM
	The motion of the bob of simple pendulum simple harmonic motion if it is given small displacement. In order to prove this fact consider a simple pendulum having a bob of mass 'm' and the length of pendulum is 'l'. Assuming that the mass of the string os pendulum is negligible. When the pendulum is at rest at position 'A', the only force acting is its weight and tension in the string. When it is displaced from its mean position to another new position say 'B' and released, it vibrates to and fro around its mean position.
	Suppose that at this instant the bob is at point 'B' as shown below :
	FORCES ACTING ON THE BOB
	1. Weight of the bob (W) acting vertically downward. 2. Tension in the string (T) acting along the string.
	The weight of the bob can be resolved into two rectangular components:
	a. Wcosq along the string. b. Wsinq perpendicular to string.
	Since there is no motion along the string, therefore, the component Wcosq must balance tension (T) i.e.                                                                      Wcosq = T
	This shows that only Wsinq is the net force which is responsible for the acceleration in the bob of pendulum.
	According to Newton's second law of motion Wsinq will be equal to m x a
	i.e.                                                                      Wsinq = m a
	Since Wsinq is towards the mean position, therefore, it must have a negative sign. i.e.                                                                     m a = -  Wsinq
	But W = mg
	m a = -  mgsinq
	a = -  gsinq
	In our assumption q is very small because displacement is small, in this condition we can take sinq = q
	Hence                                                                     a = -  gq ----------- (1)
	If x be the linear displacement of the bob from its mean position, then from figure, the length of arc AB is nearly equal to x
	From elementary geometry we know that:
	Where s= x, r = l
	Putting the value of q in equation (1)
	As the acceleration of the bob of simple pendulum is directly proportional to displacement and is directed towards the mean position, therefore the motion of the bob is simple harmonic when it is given a small displacement

THERMAL CONDUCTIVITY

THERMAL CONDUCTIVITY
Thermal conductivity is defined as" the amount of heat conducted in one second through one cubic meter of a substance whose two opposite faces are maintained at the temperature difference of one degree centigrade." It is denoted by "K". Formula K=QL/ADTt Unit : Unit of thermal conductivity is J/mKs OR watt/m.K.
EXPRESSION FOR THERMAL CONDUCTIVITY
Experiments indicates that the amount of heat conducted through a solid block is :  Directly proportional to temperature difference between two faces of block.
DQ a DT ...................... (i)
Directly proportional to the area of cross - section of block.
DQ a A ...................... (ii)
Directly proportional to the the time interval to which heat is conducted.
DQ a t ...................... (iii)
Inversly proportional to the length of block.
DQ a 1/L ...................... (iv)
Combining above facts,we get
DQ a DT.A.t /L
OR
OR

CIRCULAR MOTION AND GRAVITATION

GRAVITATION
Every object in our universe attracts the other object with certain fore towards its center. This force of  attraction is known asGRAVITATIONAL FORCE and the phenomenon is called GRAVITATION. This is  gravitational force which is responsible for the uniformity or regularity in our daily astronomical life. The  whole system of the universe is in order only due to this force. Due to gravitation, the system of our  universe is working uniformly and smoothly. The planets around the earth or around the sun moves in an  orderly motion due to gravitation.
NEWTON’S LAW OF GRAVITATION
In order to explain the gravitational force between two bodies, Newton formulated a fundamental law known after his name i.e. "NEWTON'S LAW OF GRAVITATION" Newton’s law of gravitation states that every object in the universe attracts the other object with a force and :
(1) The gravitational force of attraction between two bodies is directly proportional to the product of their  masses.
F a m1 x m2 ------- (1)
(2) The gravitational force of attraction between two bodies is inversely proportional to the square of the  distance between their centers.
F a 1/d2 --------- (2)
MATHEMATICAL REPRESENTATION
Combining (1) and (2)
F a m1m2 /d2
F = G m1m2/d2
Where G = universal gravitational constant
Value of G:
G = 6.67 x 10-11 Nm2/kg2
MASS OF THE EARTH
Consider a body of mass ‘m’ placed on the surface of the earth. Let the mass of the earth is ‘Me’ and  radius  of earth is ‘Re’ .
Gravitational force of attraction between earth and body is
F = G m Me/ Re2
We know that the force of attraction of the earth on a body is equal to weight the weight of body.
i.e
F = W
therefore
W = G m Me/ Re2
But W = mg
mg = G m Me/ Re2
or g = G Me/Re2
or Me = g x Re2/G
From astronomical data:  g= 9.8 m/s2  Re = 6.4 x 106 m  G = 6.67 x 10-11 N-m2/kg2  Putting these values in the above equation.
Me = 9.8 (6.4 x 106)2/6.67 x 10-11 or

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.

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

MULTIPLICATION & DIVISION OF VECTOR BY A NUMBER (SCALAR)

MULTIPLICATION OF A VECTOR BY A SCALAR
When a vector is multiplied by a positive number (for example 2, 3 ,5, 60 unit etc.) or a scalar only its magnitude is changed but its direction remains the same as that of the original vector. If however a vector is multiplied by a negative number (for example -2, -3 ,-5, -60 unit etc.) or a scalar not only its magnitude is changed but its direction also reversed.
The product of a vector by a scalar quantity (m) follows the following rules:
	(m)  = (m) which is called commutative law of multiplication.
	m(n) = (mn) which is called associative law of multiplication .
	(m + n) = m+ n which is called distributive law of multiplication .
	DIVISION OF A VECTOR BY A SCALAR
	The division of a vector by a scalar number (n) involves the multiplication of the vector by the reciprocal of the number (n) which generates a new vector.
	Let n represents a number or scalar and m is its reciprocal then the new vector  is given by :
	where m = 1/n
	and its magnitude is given by:
	The direction of  is same as that of if (n) is a positive number.  The direction of  is opposite as that of if (n) is a negative number.

ADDITION OF VECTORS

ADDITION OF VECTORS4

PARALLELOGRAM LAW OF VECTOR ADDITION
Acccording to the parallelogram law of vector addition:
"If two vector quantities are represented by two adjacent sides or a parallelogram then the diagonal of parallelogram will be equal to the resultant of these two vectors."
	EXPLANATION
	Consider two vectors . Let the vectors have the following orientation
	parallelogram of these vectors is :
	According to parallelogram law:
	MAGNITUDE OF RESULTANT VECTOR
	Magintude or resultant vector can be determined by using either sine law or cosine law.