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DEFINITIONS
Physics: Physics is the study of properties of matter and energy along with the interaction between them is called physics.
Branches of Physics: 1. Atomic physics 2. Nuclear physics 3. Molecular physics
4. Solid state physics 5. Quantum
physics 6. Relativity physics 7. Low temperature physics 8. Austro physics 9. Bio physics 10. Geo physics 11. Plasma
physics
12. Particle physics.
Dimensions: Dimension of a physical quantity of the power of fundamental quantity in terms on which it can be represented.
Each of the basic quantities is called dimension.
SIGNIFICANT: The number of accurately digit and first doubtful digit are known as significant figure.
SCALAR: Those physical quantities which are completely specified by their magnitude are called Scalar. Scalar can be
added, subtracted, multiplied and divided by using the rules of elementary algebra. e.g. length, mass, time, speed etc.
VECTOR: Those physical quantities which are completely specified by their magnitude as well as direction are called
vectors. Vectors can be added, subtracted, multiplied and divided by using the rules of vector algebra. E.g. displacement,
velocity, acceleration, force etc.
UNIT VECTOR: A vector whose magnitude is unity in the direction of a given vector is called “unit vector”. It is denoted
by
.
DISPLACEMENT: Displacement refers to “change of position” of a body. It is a vector quantity.
MOTION: When a body does not change its position with respect to its surrounding it is said to be at “rest”. But when a
body changes its position with respect to its surroundings, it is said to be in motion. In face, all the states of rest and motion
are relative. There are three types of motion. Translator motion, rotatory motion and oscillatory motion.
SPEED: Speed of a moving body is the distances covered in unit time. Speed is a scalar quantity. It is not same as velocity.
Speed is always opposite. The word speed refers to instantaneous speed.
TENSION: When an object is suspended by a string, the force that acts along the string and equal in magnitude but opposite
in direction to the weight is called tension.
VELOCITY: (average velocity). It is defined as the rate of change of displacement of a body. OR the rate of change of
displacement is called velocity.
Symbolically,
ACCELERATION: Whenever the velocity of a body changes, it is said to be possess acceleration, OR the rate of change of
velocity is called acceleration. There are four types of acceleration. Average acceleration, instantaneous acceleration, uniform
acceleration and non-uniform acceleration.
FRICTION: When a body is in motion a rough surface or through a viscous medium (e.g. water or air), there is resistance to
motion. This resistance is called friction. There are two types of friction. Solid friction and fluid friction.
SOLID FRICTION: When one solid body moves across the surface of another side, there is always resistance which tends
to oppose nay relative motion between the two surfaces in contact. This opposing force is called “friction”. REASON: The
friction is due to the roughness of the material surfaces in contact. The ‘elevations’ of one surface get interlocked with the
‘depression’ of the other surface. Thus they oppose relative motion. Friction is a ‘statistical concept’. It involves electrostatics
forces between large number of molecules where surface are in contact.
FLUID FRICTION: When a solid body moves through a fluid (viscous medium), it experiences an opposing force on the
body, called “fluid friction” or “viscous drag” or “viscosity”. This force depends on the dimensions and velocity of the body
with respect to a fluid (liquid or gas).
PROJECTILE MOTION: Let a body be thrown in horizontal with a uniform velocity, under gravity. It is subjected
simultaneously to (1) Uniform horizontal motion with constant velocity. (2). A changing vertical motion with constant
acceleration (a = g). Then its path is a curve called parabola. The body is called projectile, and the path traced by a body is
called projectile.
(Ram Kumar)
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TRAJECTORY OF PROJECTILE: The path followed by a projectile is called its ‘trajectory”. The position of the
projectile, at any instant, can be determined by calculating “x” and “y” components of its displacement.
UNIFORM CIRCULAR MOTOIN (U.C.M): When a body is moving at a constant (uniform) speed in a circle, it is said to
possess uniform circular motion (U.C.M). Circular motion is an example of motion in two dimensions. In this motion, both
velocity and acceleration are constant in magnitude but both change their directions velocity and acceleration constant in
magnitude but both changes their direction continuously. For example, motion of a stone tied to a string and whirled in a
circle motion of the moon round the earth, automobile wheel, revolution of computer disc etc.
ANGULAR DISPLACEMENT: The angle subtended by a body in a circular motion is called “angular displacement”. It is
denoted by . Its SI unit is radian. RADIAN: One radian the angle subtended at the center of a circle by is whose length is
equal to the radius of the circle.
ANGULAR ACCELERATION: It is defined as the rate of change of angular velocity. It is denoted by
.
INSTANTANEOUS ANGULAR ACCLERATION: It is defined as the limiting value of average angular acceleration went
e time interval is infinitesimally small. It is denoted by
. NOTE: The term “angular acceleration” means instantaneous
angular acceleration.
CENTRIMETAL ACELERATION: Consider a body tied to one end of a string. Let it be whirled in a horizontal circle.
The linear velocity of the body at any instant is directed along the tangent to its circular path. As the body moves along the
circumference, the magnitude of the velocity remains constant, but the direction of the velocity changes. Change of
displacement of the body from P to Q shows that it has velocity. As the directions of the velocities are changing, so it
possesses an acceleration. Since the magnitude of the linear velocity remains constant, the direction of this acceleration must
not be in the direction of motion. It will be perpendicular to the circular path and is always directed towards the centre of the
circle. It is called “centripetal acceleration”. It is denoted by
. As the direction of the centripetal acceleration is changing,
so the acceleration is not constant.
TORQUE: The turning effect of an object due to an applied force is called “torque” or “moment of force”. Torque ( T)
depends upon (1) magnitude of force applied (F) (2) the perpendicular distance of the line of action of the force from the axis
of rotation (or fulcrum or pivot), also called “moment arm” or “lever arm”(d). Symbolically, torque T = Fd
EQULIBRIUM: If a number of force act one body such that the resultant is zero, then the body is said to be in equilibrium.
A body in equilibrium possesses zero linear and zero angular acceleration.
STATICS: The branch of mechanics that deals with bodies acted upon by a number of forces but are in equilibrium is called
“Static”.
ANGULAR MOMENTUM: The angular momentum of a body about an axis is defined as the cross product of position
vector
and linear momentum
.
WEIGHT: Weight of a body is the force due to gravitational attraction of the earth upon its mass. Thus W or
= mg. The
weight of on abject is the force of gravity on it. It is not a fixed quantity. It varies from place to place.
WEIGHTLESSNESS: Weight of a body in a certain frame of reference is equal but opposite to the force required to prevent
it from falling in that reference frame. In an inertial frame, the weight of a body is equal to the force of gravity. In an
accelerated frame, the weight depends upon the acceleration of the frame. If no force is required to hold an abject from falling
in a frame of reference, it is the absence of restraining force which gives the impression of weightlessness.
ARTIFICIAL GRAVITY: To an astronaut, weightlessness in a satellite space ship or space laboratory is highly
inconvenient. To overcome this problem an artificial gravity can be created by spinning a space-craft around its own axis.
Rotating space ship supplies artificial gravity for the astronaut. So, the apparent weight is the same as on the earth.
WORK: when a force is applied on a body. It moves trough a certain distance, then it is said that some work has been done.
Work is a scalar quantity. MATHEMATICALLY:
WORK DONE AGAINST GRAVITIONAL FIELD: Gravitational force is the force with which the earth attracts a body
towards its centre. It is equal to the weight of the body. It can do positive or negative work. Work is positive if a body moves
in the direction of the gravitational force, i.e. towards the centre of the earth. Work is negative if a body moves against the
direction of gravitational force.
POWER: Average power of an agency is defined as “rate of doing work” or “rate of transfer of energy”.
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(Cell no: 0323-3839694)
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Symbolically,
Where
= amount of work (or energy)
= time interval.
ENERGY: Energy is the capacity of doing work by an agency work. A body possessing energy can exert force on any other
body to work. Also when work is done on a body, an equal amount of energy is stored in it. Forms of energy: mechanical
energy, heat energy, light energy, sound energy, magnetic energy, electrical energy, chemical energy, nuclear energy etc.
KINETIC ENERGY: The energy possessed by a body due to its motion is called “kinetic energy” (K.E).
POTENTIAL ENERGY: The energy possessed by a body due to its position or state is called “potential energy (P.E).
VIBRATORY MOTION: (oscillatory motion). When a body moves to-and-fro about its mean position, it is said to possess
“vibratory motion” or “oscillatory motion”.
SOME TERMS: 1. Periodic motion: A motion which repeats itself in equal intervals of time is called periodic motion.
Vibratory motion and circular motion are both periodic motion. 2. Vibration: One complete round trip of a body is called
vibration. Let mean position of a pendulum be O. one vibration is its motion from A to O, then from O to B., them from B to
O then back to A. Time period: It is the time required to complete on vibration. Its unit is second. Frequency: It is the
number of vibrations executed by a body in one second. Displacement: It is the distance of a vibrating body from its mean
position at an instant. Amplitude: It is the maximum displacement of a vibrating body from its mean position.
SIMPLE HARMONIC MOTION: If a body is in vibratory motion such that: 1. its acceleration is directly proportional to
displacement from a fixed point. 2. the acceleration is directed towards the mean position of equilibrium, then the body is
said to execute simple harmonic motion (S.H.M). Mathematically: a a - x.
SIMPLE PENDULUM: An ideal simple pendulum consists of a point mass suspended by a weightless, inextensible and
perfectly flexile string from a rigid, frictionless support. Consider a physical pendulum. It consists of small bob suspended
from a rigid support by a thin, inelastic thread.
ANALYTICAL TREATMENT OF WAVE: A wave is a disturbance that moves through a medium in such a manner that
at any instant displacement is a function of position and time. y = f (x-t). it is called wave function.
ENERGY AND POWER IN WAVSS: Wave consist energy. Consider a harmonic wave traveling along a string. Since
every point on the string moves vertically up or down, thus every segment of equal mass has the same energy. The energy of
the segment is entirely P.E., but the energy of the segment W is entirely of equal mass has the same energy.
PRINCIPLE OF SUPERSUPERPOSITION OF WAVES: When two or move wave travel in medium, the net
displacement the medium caused by the resultant wave at any point is given by the algebraic sum of separate displacements
of all the waves. For n waves, the resultant displacement is:
Explanation: Consider two
waves of the same amplitude, wave length and frequency, which differ in phase by .
STANDING WAVES: When two exactly similar waves traveling between two fixed points along the same line but in
opposite directions with equal velocities, superpose each other, they produce “stationary waves”. There are two kinds of
wave: transverse stationary wave: when the component waves are transverse, e.g. waves produced due to wiggling of a cord
fixed to one end; or waves between bridges of a sonometer. Longitudinal stationary.
Waves: when the component waves are longitudinal, e.g. waves set up in a vibrating air column.
SONOMETER: Sonometer is a device used to produces desired number of loops in a stretched wire. It can be made to
vibrate. The laws of vibrating strings can be verified experimentally.
SOUND WAVES: Sound waves are compression waves traveling through a compressible medium (e.g. air). Longitudinal
waves are produced when the particles of a medium are disturbed parallel to the direction of propagation of waves.
Longitudinal waves are the result of regular succession of compressions and rarefactions in a medium.
SPEED OF SOUND: Sound waves are longitudinal waves traveling through a compressible medium solid, liquid and gas. A
mechanical wave is transmitted by the vibrations of the particles of the propagating medium. The speed of sound depends
upon two factors: elastic property and inertial property.
MUSICAL SOUND: Sound that is produced due to periodic, regular and long continued, mechanical disturbances produces
consonance. It is known as “musical sound”. Sound that is produced due to non-periodic, irregular and short mechanical
disturbances produces dissonance. It is known as “noise”.
CHARACTERISTICS OF MUSICAL SOUND: there are three characteristics of a musical sound or note: 1. intensity 2.
pitch and frequency 3. quality
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INTENSITY OF LOUDNESS: intensity of sound is the rate of transfer of energy per unit area on a surface perpendicular
to the direction of propagation.
SYMBOLICALLY:
Where E is the energy transmitted, A is the total area, and t is the time.
LOUDNESS: Loudness of sound is the magnitude of the auditory sensation produced by sound on the hearing organ.
Loudness depends upon 1. Intensity of sound 2. Sensitiveness of sound.
INTENSITY LEVEL: The difference between the loudness L of a sound of intensity I and loudness Lo of sound of
minimum audible intensity Io is called “intensity level”.
BEATS: The periodic alternations of sound between a maximum and minimum loudness are called “beats”.
ACOUSTICS: The branch of sound in which production and characteristics of sound waves are studied in designing a hall is
called “Acoustics”. A lecture room, auditorium or a concert hall is good acoustically in which a speech or music can be heard
equally throughout the hall without troublesome echoes and reverberations.
SHOCK EAVES: when speed of source of sound (Vs) is comparable to velocity of sound waves in the medium (v), then the
source (e.g. an aero plan) keeps pace with the outgoing waves in the direction of medium. The Doppler Effect must be
modified.
NATURE OF LIGHT: Light is an electromagnetic wave. Wave theory of light can explain properties of light like reflection,
refraction, dispersion, interference, diffraction, polarization etc. But “Photo-electric effect” and “Compton effect” can be
explained using quantum theory.
INTERFERENCE OF LIGHT: When eaves from two source superpose each other, then under suitable conditions, then
reinforce each other at some points and cancel at other points. This phenomenon is called “interference”.
INTERFERENCE OF THIN FILM: A thin film is that one whose thickness is comparable with wavelength of light. E.g.
Soap bubbles, thin transparent film of glass and oil layers on water are common examples of thin films. Explanation: When
light is reflected from a thin film, we observe vivid color bands due to interference of effect. Consider thin uniform film of oil
of water. Let refractive index of air film be n. let thickness of air film be t.
DIFFRACTION: When light passes an obstacle it bends round the corners of his obstacle and spreads somewhat into the
region of geometrical shadow. This phenomenon is called “diffraction”.
DIFFRACTION GRATING: A glass plate upon which is ruled a number of equidistant parallel opaque lines is called a
‘plane transmission grating’ of just a “grating”.
X-RAY DIFFRACTION: X-rays are electromagnetic waves of extremely small wavelength. X-rays cannot
produce interference fringes with ordinary diffracting objects. A crystal, however, serves as a three dimensional grating for xrays.
POLARISATION: According to the electromagnetic theory, light wave consists of periodic variations of electric vector
accompanied by the magnetic field vector at right angle to it. The light vibrations refer to the vibrating electric field vector. A
light wave traveling at a given instant is represented by a vector line. Its direction and magnitude represents the direction and
displacement of the vibrating electric field .Such a line is called “light vector”.
MIRRORS: Reflection: when light falls on a smooth and polished surface, it is turned back in the same medium. This
phenomenon is called “reflection”.
LENSES: Refraction: when light passes form one transparent medium to another, it bents. This phenomenon is called
“refraction”. A medium is “optically dense” (has greater optical density) if light is bent towards the normal.
POWER OF LENS: power of lens is the reciprocal of the focal length expressed in meters.
OR
The unit of refractive power of a lens is the diopter (where 1 diopter = 1/meter) conventionally. A converging lens has a
positive power and a diverging lens has a negative power.
LENS ABERATIONS OR DEFECTS OF LENSES: Every image contains a number of common defeats tending to blur it.
The imperfect image are the result of the defects n shape and form of the lenses. The defects of lenses are: spherical
aberration, chromatic aberration, astigmatism, coma, distortion, etc.
SPHERICAL ABERATION: In thick lenses the focus is not a sharp point, but is containe4d in a region called “focal
region”. This produces blurred images. This is defect is called “spherical aberration”. REASON: When rays parallel to
principal axis pass through the edges of a thick lens, they are brought to focus nearer the lens. But those rays which pass
through nearer to its centre, they are brought to focus farther from the lens.
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(Cell no: 0323-3839694)
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CHROMATIC ABERRATION: In thick lenses the images formed have color at different locations. This defect is called
“chromatic aberration”. REASON: A lens may be regarded as made up of two prisms placed one above the other. Due to
dispersion of the refracting medium of the lens, different wavelengths of light focus at different points. Hence image consists
of small linear spectrum.
MAGNIFICATION: Angular magnification is the ratio of the visual angle subtended by the final image when viewed
through a lens () to the visual angle subtended by the object placed at same distance, when viewed by an unaided eye ( ).
TYPES: there are two types of magnification. 1. Linear 2. Angular magnification.
COMPOUND MICROSCOPE: It is an optical instrument used to see near objects of very small dimensions clearly.
PRINCIPLE: A microscope is used to increase the visual angle of objects of very small size when placed at the least
distance of distinct vision (‘d’). The magnifying power may be increased by using two lenses. 1. Objective lens 2. Eye piece
lens.
ASTRONOMIAL TELESCOPE: It is an optical instrument used to view the heaven by bodies (e.g. planets, stars etc.
PRINCIPLE: It apparently increases the visual angle. The image of a distant object is smaller but it looks larger through a
telescope because it is much nearer to the eye and has a large visual angle.
TERRESTRIAL TELESCOPE: it is an optical instrument used to view distant objects on the earth clearly.
THE EYE: The eye is a complex part of the human body. It is an optical system which resembles a camera. The eyeball is
almost spherical in shape. TYPES: sclera, cornea, iris, pupil, retina.
(Ram Kumar)
(Cell no: 0323-3839694)