Physics is a branch of science which deals with the properties of matters

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Physics:

Physics is a branch of science which deals with the properties of matters.

Physics is divided into Several parts :

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(1) General Physics, (2) Heat, (3) Sound, (4) Magnetism (5) Electricity and (6) Modern Physics etc.

Three states of matter-

On the basis of physical properties of matter, it has been divided into three states-solid, liquid and gas.

Solid A solid has a definite shape and volume.

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Liquid-A liquid has a definite volume but no definite shape,

Gase

A gas has neither definite shape nor definite volume.

Terms used in General Physics:

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Density

Density of a substance is mass per unit volume.

Motion-

When it is said that a body is in motion, it is meant that it is changing its position with respect to some other body.

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Speed

Speed is the distance travelled by an object per unit of time.

Velocity-It is the distance travelled by an object in a given direction per unit of time.

Accelaration

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It is the rate of change of velocity.

Scalar Quantity-

A quantity which has only magnitude and direction is known as scalar quantity. Such as mass, speed etc.

Vector Quantity

A quantity which has magnitude and direct both is called vector quantity. Such as velocity, acceleration

Force

Force is that which changes or tends to change the of rest or motion of a body.

Force = mass x acceleration.

Mass

The mass of a body is a measure of the quantity of matter the body. Mass is always constant, being independent of its 5urroundings and position.

Weight-The weight of a body is the force with which the earth I attracts the body towards itself.

Newton’s first law of motion

Everybody continues in its state of rest or of uniform motion in a straight line unless it is compelled to change the position by force impressed on it.

Newton’s second law of motion-

The acceleration imparted to a body by a force acting on it varies directly as the force in the direction of the force applied.

Newton’s third law of motion-

To every action there is an equal and opposite reaction.

Power

Power is defined as the rate at which work is done in

Work-When a force creates motion in a body it implies work has been done, i.e. work is done by a moving force. It is equal to the product of the force and the distance. It moves along its line of action.

Work Force x Distance or W = F.S.

Energy

The capacity of doing work of a body is called energy.

Kinetic energy-

The energy possessed by a body due to its motion is called kinetic energy.

Potential energy-

The energy possessed by a body owing to its Position is called potential energy.

Momentum

Momentum is the composite effect of mass and velocity of a body.

M = mass x velocity.

Centripetal force-

It is the force acting towards the centre and pulling the object into a circular path. .

Centrifugal force-

It is the fictitious force which appears to act an object moving in a circular path.

Friction

Friction is a force that resists the movement of one surface over another.

Surface tension

Surface tension is a force acting on surface acting on the surface of the liquid.

Elasticity-

A body that returns to its original shape and size c the removal of the deforming force is called elastic and this property, of the body is called elasticity.

Law of conservation of Energy-

This law states that energy can neither be created nor be destroyed but only transformed from one kind to another so that the sum total of all energy in the universe remains constant.

Heat:

Heat is a form of energy which raises temperature of matte increases volume of matter and changes state and physical property of matter and brings about chemical change.

Temperature

The degree of heat or cold of a body substances which can” be measured by various scales is called temperature.

Thermometers

Thermometers are the instruments with the help of which the temperature of a body is measured. Centigrade Fahrenheit and Reaumur are thermometers.

Conductivity

It is the transfer of heat from one molecule of; conductor to another molecule. Silver is the best conductor followed by copper.

Radiation

Radiation is the transmission of heat from one region to another without heating the medium. Sun-light travels the earth through radiation.

Convection

Convection is the transmission of heat of heated matter, i.e. by actual motion of the heated particles of a liquid or gas

Evaporation

Evaporation is the change of state from liquid to vapour and thereby results in cooling.

Latent heat-

The amount of heat required to change the state of a substance from solid to liquid or from liquid to gas without change in temperature.

Light:

Light is an electromagnetic radiation that has a wavelength in about the range of 380-780 nanometers. It is a form of energy which travels in straight lines and causes the sensation of vision.

Spectrum-

The sunlight is made up of seven band of colors When a beam of light is passed through a prism, a band of colors formed which is known as spectrum in which violet and red bands for the extremes.

Incident Rays

These are the rays of light that fall upon a body.

Reflected Rays-

These are the rays that are sent back by the year after falling on it.

First law of Reflection-

This law states that the angle of reflection is always equal to the angle of incidence.

Second law of Reflection-

The incident ray, the normal and (he reflected ray of light all lie in the same plane.

Refraction of light-

When a beam of light passes through one medium to another it gets deviated from its original path. This phenomenon is known as refraction of light.

Dispersion-

When white light is passed through a glass prism it splits into seven colors. This process is known as the dispersion of light.

Diffraction

Diffraction is the spreading of light as it passes through a narrow aperture, because light is a wave of motion. Hence, light-rays emerging from a cinema machine spread wide on the screen.

Primary colours-

These are red, blue and red.

Scattering of light

A rough surface scatters light, because each part of the surface reflects the light at different angles which is known as scattering of light. Sky appears blue due to the scattering of light.

Mirrors

Mirrors work on the principle of reflection. Mirrors are of three types :

(i) Plain Mirror-

A virtual image is formed by a plain mirror behind the mirror. It is always equal to the size of the object and erected,

(ii) Concave Mirror

Concave mirror is a type of spherical mirror. In most of the cases real inverted images are formed by concave mirror. When object is kept within the Focus and Pole of the mirror an enlarged, imaginary and erected image is formed in front of the mirror. Thus concave mirror is used for shaving purposes.

(iii) Convex Mirror

In this mirror always small, imaginary (virtual) and erected image is formed. This mirror has a wide field of view. Therefore, the convex mirror is used as a rear view mirror in vehicles.

Mirror formula:

1/f = 1/u+1/v is known as mirror formula.

Where, u = distance of the object from the mirror, v = distance of the image from the mirror and local length of the mirror.

Lens-

A lens consists of transparent medium bounded by tow non-parallel surfaces of the two spherical surface.

There are two types of lenses:

(i) Convex or Converging lens

In most of the cases real and inverted images are formed. But when the object is placed between the focus and lens virtual and erected image is formed. Convex lens is used in magnifying glasses.

(ii) Concave or Diverging lens-

In as concave lens always virtual and elected images are formed.

Lenses are used in all optical instruments like microscopes telescopes, cameras and projectors.

Lens formula- Where, v is the distance of the image from the lens, u is the distance of the object from the lens and f is the focal length of the lens.

Power of the lens-

Power of the lens is written as dioptre. Where, dioptre is the unit of the power of the lens.

Defects of the eyes

There are four types of defects in the eyes which are as follows-

(i) Short sightedness or myopia-

A person suffering from this defect can see the object clearly lying at a short distance but cannot see pre lying at a distant place. This defect of the eye can be rectified by using a concave lens of appropriate focal length.

(ii) Long sightedness or hypermeiropia-

A person suffering from this defect can see the object clearly situated at a distant place but cannot see distinctly lying, at a short distance. This defect of the eyes can be corrected by using a convex lens of appropriate focal length.

(iii) Astigmatism-

A defect of an optical image in which the rays passing through the lens, focus in different planes. This defect is caused due to unusual curvatures of cornea aberration in the lens. This defect of the eye can be rectified by using cylindrical lens.

(iv) Presbyopia-

The defect of vision because of which neither near objects nor distant objects are clearly visible. It is caused by the weakening of eye muscles in old age. This defect corrected by the bifocal arrangement.

Speed of light

Speed of light in vacuum is 3 x 108 meter/sec. I denser medium the speed of light decreases.

Sound:

Sound waves-

Sound waves are mechanical longitudinal waves and require a material medium, whether solid or liquid or gas for their propagation. Thus the sound waves cannot pass through vacuum.

Ultrasonic waves-

These are those mechanical waves having frequency above 20,000 Hz are called the ultrasonic waves.

Infrasonic waves

These are those mechanical waves having frequency below 20 Hz are called the Infrasonic waves.

Audible range of sound

Human beings can listen only those wave the frequency of which ranges from 20 Hz to 20,000 Hz and this frequency range is known as “audible range of sound.”

Speed of sound-

The speed of sound depends upon the nature of the Carrier media. In dry air at 0°C the speed of sound is 330 meter/sec. The speed of sound in solid medium is higher than that of liquid and gases. And the speed of sound in liquid is more than the speed in gases.

Reflection of sound

Reflection of sound waves into new directions by a surface is known as “reflection of sound.”

Refraction of sound

It is the change of direction of a sound wave on passing from one medium to another.

Echo-

Repetition of sound by reflection is known as echo.

The effect of sound remains on human ear for l/10th of a I second.

Magnetism:

Magnet is a substance which has the property of attracting pieces of iron, cobalt and nickel and when freely suspended, it points towards the north and south.

Magnetic field

The field in which the effects of a magnet or the magnetic effect of an electric current is experienced.

Magnetic meridian-

The vertical plane passing through the axis of a freely suspended magnet is earth’s magnetic field.

Angle of declination

The angle between magnetic meridian and geographical meridian is called angle of declination.

Electricity:

Electric charge-Electric charge can neither be created nor can be destroyed. It is an internal property of some elementary particles, for examples-electrons, protons.

Neutral body

Neutral body has equal number of electrons and protons.

Electric currant

Charge in motion constitutes electric current. It is measured by the rate of flow of charge.

Ohm’s law

At constant temperature the current flowing in a conductor is directly proportional to the potential difference across its ends.

Unit of electrical energy consumption

Electrical energy consumption in is measured in Kilo Watt Hour.

Transformer

Transformer is a device with the help of which A.C. of low voltage and high current is transformed into high voltage and low current and vice-versa.

Step-up Transformer-

It transforms A.C. of low voltage and high current into high voltage and low current.

Step-down Transformer-

It transforms A.C. of high voltage and low current into low voltage and high current.

Alternating Current (A.C.)-

It changes in magnitude and in direction with time.

A.C. Generator

It is based upon electromagnetic induction. It converts mechanical energy into electrical energy.

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