Why Quantum mechanics?

                                       Quantum Mechanics Basic concepts

Why Quantum mechanics?

Before discussing the Quantum physics we have to go through Classical mechanics
Fault Concepts of classical mechanics which leads to quantum mechanics
1. According to Newton for every motion there is a reason for it. It is called the cause and effect relationship
2.If you now the exact position and velocity of the moving object we can predict its position in future and past with certainty.
3. According to classical theory there is no uncertainty in any phenomenon, it is the determinism of classical mechanics
4.Energy can be transfered from one place to another either  as particle or as waves.These forms cannot merge together
5.Measurement is perfect if the working condition of the measuring device is perfect. The error in measurement take place only by the fault of measuring device

solvay conferences
Einsteens quantum statistical interpretation
coppen hagen interpretation
maxwells kinetic theory of gases
boltmans statistical mechanics
probability theory of gases
black body radiation
ultraviolet catastrophe
photo electric effect
bright line light spectra
emission spectra
absorption spectra
rutherford atom model
bhor atom model
sommerfield atom model
paulis exclusion principle
de broglie dual wave

                       PHOTO ELECTRIC EFFECT

The emission of electrons from the surface of the certain substances mainly metals, when they are illuminated by electro magnetic waves.

The alkali metals like lithium, sodium, potassium emit electrons when exposed with visible light. Ultra violet rays eject electrons from Zinc and magnesium. Infra red rays emitted photo electrons from caesium. This effect is first discovered by Heinrich Hertz

FRAME OF REFERENCE,LIMITATIONS OF NEWTONS LAW,CARTESIAN COORDINATE SYSTEM,fictitious force

MOTION AND REST

If the position of a body changes with time ,the body is in the state of motion. If the position of the body does not changes with time it is said to be at rest.

ABSOLUTE MOTION

when the motion of a body is observed with respect to a point which is stationary in space is called absolute motion. But in universe no point is stationary. So absolute motion is an imaginary concept.

MOTION IS RELATIVE ie we can define motion relative to other bodies.

FRAME OF REFERENCE

A tree on the ground is at rest relative to earth. But it is in motion relative to sun.So in order to describe motion we first select one frame

         If we imagine a co ordinate system attached to a rigid body and we describe the position of any particle in space relative to it. Then such a co-ordinate system is called frame of reference. for location of the object the position vector are drawn from the origin of co-ordinate system. The origin may coincide with the position of observer or not But an observer uses a frame of reference which is stationary relative to him.

CARTESIAN COORDINATE SYSTEM

For the location of an event in a frame of reference we require its position and time of occurrence. Therefore 4 coordinates are required(x,y,z,t). It is called space-time frame of reference.We select a frame of reference in which the motion is easy to describe.

Example

1)A man sitting in the train throw a ball vertically upwards, with respect to an observer sitting in train the path of ball is vertically straight line. But an observer outside the train the path of ball is parabolic.

 The frame of observer in train is simple with describing the motion of the ball

2)To describe the motion of planets in the frame with respect to earth is very complicated. But the frame situated in on sun is very simple. Now the motion of all planets are circular

3)Motion of a point on a slow moving wheel of a car. If the frame is on the center of wheel, then the motion of point is circular. But frame situated on earth the motion of point is cycloid.

LIMITATIONS OF NEWTONS LAW

According to Newton's first law a body continues its state of rest or uniform motion in a straight line unless compelled by an external force.

This law violates when the observer is in an accelerated frame. Suppose if the object is at rest and the observer is on an accelerated frame, he can observe the object with negative acceleration and he at rest. A fictitious force is acting on the body.

   So Newton introduced an inertial frame , which is not accelerated relative to fixed stars and his laws are valid only in inertial frame.

    

LAWS OF THERMODYNAMICS

SYSTEM & SURROUNDINGS

System refers to the part of universe chosen for our study

The portion of universe excluded from the system is called surroundings

Types of systems

open system

A system which can exchange both matter and energy  with its surroundings is called open system.

Eg: hot coffee kept in a open vessel

Closed system

A system which can exchange  energy but not matter is  with its surroundings is called open system.

Eg: hot coffee kept in a closed vessel with conducting walls

Isolated system

 A system which can neither exchange  matter or energy  with its surroundings is called open system.

Eg:hot coffee kept in a thermos flask

  STATE FUNCTION & PATH FUNCTION

Property of a system depends only on the state of system and not depend on the path along which that state is attained is called state function

Eg:Pressure , volume , temperature

Property of a system which depends on the path along with the state is attained

is called path function

Eg: work, heat

INTENSIVE & EXTENSIVE PROPERTIES

Properties which are independent of amount of matter present in a system is called intensive properties

Eg:Pressure , viscosity , temperature

Properties which are dependent of amount of matter present in a system is called intensive properties

Eg: Mass, Volume , Energy

ENERGY OF A SYSTEM

Energy of a system is its capacity to do work. When a system does work, its energy is reduced and when work is done on a system its energy increases.

ADIABATIC & ISOTHERMAL PROCESS

A process in which no heat enters or leaves the system is called an adiabatic process. In such process the system is completely insulated from the surroundings.

An isothermal process is one which the temperature of the system remains constant throughout.In such a system energy can exchange to surroundings

ENDOTHERMIC & EXOTHERMIC PROCESS

process which liberates energy as heat is called an exothermic process

process which liberates energy as heat is called an exothermic process

REVERSIBLE PROCESS & IRREVERSIBLE PROCESS

A reversible process is one which is conducted infinitesimally slowly such that at every stage the driving force is only infinitesimally greater than the opposing force.. Such a process can be reversed by increasing the opposing force by an infinitesimal amount.
A process in which the driving force at any stage is greater than the opposing force is called an irreversible process.
All natural forces are irreversible.
INTERNAL ENERGY OF A SYSTEM(E)
The internal energy is the sum of total energies associated with the translational,rotational, vibrational,electronic, and nuclear motions at the molecular level as well as potential energy of interaction between constituent particles.

ENTHALPY(H)

Enthalpy is the sum of internal energy and pressure volume energy.
H=E+PV

THE ZEROTH LAW

Two systems that are both in thermal equilibrium with a third system are in thermal equilibrium with each other

FIRST LAW OF THERMODYNAMICS

Energy can neither be created nor destroyed it  may be converted from one form to another

SPONTANEOUS PROCESS

A  process which has a natural urge to take place by itself under a given set of conditions.

ENTROPY

Entropy is a measure of disorder or randomness in a system.

Greater the entropy greater the disorder

SECOND LAW OF THERMODYNAMICS

The entropy of the universe remains constant in a reversible process where as it increases in a irreversible process

GIBBS FREE ENERGY

It is the maximum amount of energy available with a system that can be converted into useful work or free energy the measure of the capacity of a system to do useful work
G=H-TS(Gibbs -Helmholtz equation)
A process should be spontaneous only if the free energy change is negative.

 JOULE THOMSON EFFECT

When a gas under high pressure is allowed to explain under adiabatic conditions through a porous plus in to a region of low pressure, there occur  a change in its temperature. When a gas expands adiabatically some work is done by the gas to overcome the van der waals  force of attraction between molecules.This is done at the cost of the kinetic energy of the gaseous  molecules.Then the internal energy decreses the temperature decreases

PRIMARY CELLS -voltaic cell,daniel cell

                          PRIMARY CELLS

Cells which gives the electrical energy by irreversible chemical reaction is called primary cell .primary cells are not rechargeable.

VOLTAIC CELL

A voltaic cell consist of of copper and zinc electrodes dipped in dilute sulphuric acid.The positive charges accumulate on the copper electrode and negative charges on the zinc electrode.This is because the electrolyte decomposes in to H ions and Sulphate ions. The negatively charged sulphate ions move towards Zn and Zn loses two electrons and become ZnSO4 .Positively charged Hydrogen ions move towards Cu and accept two electrons and hydrogen gas is liberated.

When the circuit is closed the Cu is at higher potential and Zn is at lower potential. Current flows from Cu electrodes to Zn electrode in the external circuit. The emf of the cell is 1V.

 DANIEL CELL

Danial cell consist of a copper vessel containing copper sulphate solution. The wall of the vessel is the positive electrode. A porous pot containing dilute sulphuric acid is placed in the CuSO4 solution. The Zinc rod is immersed in dilute sulphuric acid. This is the negative electrode.

The porous pot allows the ions to pass from one solution to other but prevents the mixing of the solutions.Oxidation take place at Zinc rod.The Zinc ions move to the copper sulphate solution through the porous pot and combine with sulphate ion to form zinc sulphate.

Cu ions move towards the copper vessel and are deposited there.The reduction reaction take place

diagram

sound-loudness,intensity,pitch,timbre

                                       SOUND

HOW IS SOUND TRANSMITTED THROUGH A MEDIUM?

Sound is produced by the vibration of the object.Sound needs a material medium to travel.Sound waves are longitudinal waves. In longitudinal waves the particles of the medium vibrates back and forth in the same direction.

Wave length

The distance between two nearest points in a wave which are in the same phase of vibration is called wavelength./ or the distance between the centers of two consecutive rarefactions or two consecutive compressions is called wavelength.

Frequency

Number of vibrations per second is called frequency. Unit Hertz

Velocity

The distance traveled by sound in one second  unit m/s

Velocity v=frequency*wavelength

DIFFERENCE BETWEEN MUSIC AND NOISE

Sound produced by regular vibrations and pleasing to hear is called music

Unpleasant sound produced by irregular vibrations is called noise

 One person feels a particular sound as a music but the other person feels it as noise. So there is personal difference

CHARACTERISTICS OF SOUND

INTENSITY

The amount of sound energy passing each second through unit area is called the intensity of sound.Increasing the amplitude of sound wave increase the intensity.

Intensity of sound is proportional to the square of the amplitude of sound.

Unit W/m^2.

Does the natural frequency of the diaphragm change for the gentle and the strong taps?

The amplitude of vibration changes. But the natural frequency of vibration remains the same.

LOUDNESS

No two persons will not have the same experience of hearing. The intensity of sound produced in the ear is called loudness. Loudness the measure of the response of the ear. loudness is the measure of audibility produced by sound in a person. Unit dB

Factors affecting loudness

Amplitude: Loudness is directly proportional to square of the amplitude of vibrating body.

Surface area: Loudness is proportional to surface area

Distance between source and receiver

 Loudness is inversely proportional to the square of the distance between the source and receiver.

Density of the medium

As density increases loudness increase

If wind is blowing in the direction of propagation of sound loudness increases,otherwise loudness decreases.

PITCH

Shrillness of a sound felt by ear is its pitch.Pitch depends on frequency of sound.

Sounds of higher frequency is called high pitch

sound with lower frequency is called lo pitch

Examples of high pitch sound: Creeping of cricket, sound of woman, sound of children

Low pitch sound:sound of man, sound of drum, sound of beetle,sound of cow

BASS &TREBLE

A group of sound waves of low pitch is bass

A group of sound waves of high pitch is treble

TIMBRE OR QUALITY

This enable us to distinguish one sound from another having the same pitch and loudness.

SOUND OF A PERSON

Loudness is controlled by the flow of air coming from the lungs through larynx.The frequency of sound is controlled by the tension and vibration of larynx. But the quality depends on the resonators.(Nose,moth,throat,empty spaces in side the mouth)

RESONANCE

When a body under forced vibration,if the frequence of the impressed vibration is equal to the natural frequency of the vibrating object, then the amplitude of the vibation is maximum. This phenomenon is called resonance.

Experiments to prove resonance:- Sonometer , Resoanance column

reflection,refraction,total internal reflection,fibre optics

                                 REFLECTION

when a ray of light is incident on a mirror it gets reflected in accordance with the following laws

First law

The incident ray, the reflected ray and the normal at the plane of incidence all lie in the same plane

Second law

The angle of incidence is equal to angle of refraction

LATERAL INVERSION

The sideways reversal of the image formed by a plane mirror is known as lateral inversion

 

 REFRACTION

 The phenomenon of bending of light from its straight line path as it passes from one medium to another with  change in density

LAWS OF REFRACTION

FIRST LAW

The incident ray,the refracted ray, and the normal to the surface of separation at the point of incidence all lie in the same plane.

SECOND LAW

The ratio of the sine of angle of incidence and the sine of angle of refraction is constant  for a given pair of media

sin i/sin r =constant ,This constant is called refractive index(RI)

Another equation for RI= Speed of light in vacuum/Speed of light in medium

On what factors does the refractive index of a medium depend?

Nature of medium

nature of surrounding medium

wavelength of light used

temperature

REFRACTION THROUGH GLASS SLAB

TOTAL INTERNAL REFLECTION

It is the Phenomenon in which a ray of light traveling at an angle of incidence greater than the critical angle from a denser to rarer medium is totally reflected back into the denser medium,obeying laws of reflection

The angle of incidence in the denser medium for which the angle of refraction in the rarer medium is 90'

APPLICATIONS OF TOTAL INTERNAL REFLECTION

1 Sparkling of Diamond

2.Mirage formation

 It is an optical illusion obseved in deserts or over heated surfaces, due to which observer sees a pond of water at some distance. The lower layer of air near earth surface get heated  than the upper layer then at lower layer density of air is less.So refraction take place from rarer to denser medium

LOOMING

This mirage observed in cold region. The lower  layer of air is cooler an denser while upper layer is hotter and rarer. When refraction of light take place the ships appears to hang inverted in the air

3.Optical fiber - Used to transmit light through long distance

4.periscope, binoculars

5.Reflector light of Bicycle

EXPLAIN THE PHENOMENON OBSERVED IN NATURE DUE TO REFRACTION
1. The sun is visible to us about 2 minutes before and actual sunrise

2.A fish at the bottom of the tank appears to be raised its position.

3.AN OBJECT PLACED AT THE BOTTOM OF BEAKER APPEARS TO BE RAISED
4.Twinkling of stars is due to refraction of its light passes through different layers of atmosphere with different densities

LIGHT THEORIES-CORPUSCULAR,WAVE,ELECTROMAGNETIC,QUANTUM,PHTOELECTRIC

                                LIGHT

Different Theories

Corpuscular theory

By Isaac Newton

Light emitted from a source is  the flow of very minute, elastic, invisible , spherical shaped corpuscles. This theory can explain Rectilinear propagation of light,Reflection and Refraction.                                                                                       Newton's fault on explanation of Refraction

Newton argued that the velocity of light increases with increase in density of medium. But Leon Foucault invented light has maximum speed in vacuum

This theory cannot explain Interference, Diffraction and color vision

Wave Theory of Light

By Christian Huygens

Light is propagated in the form of waves. Like sound wave light is also a longitudinal wave also composed of compression and Refraction

This theory can easily explain Diffraction, Reflection, Refraction

 Famous Scientist Thomas Young done a lot of experiments on Optical Phenomenon

Correction of Wave theory

By Augustin Fresnel

Gives a satisfactory explanation of Diffraction, linear propagation based on wave theory. He find out light is Transverse wave instead of longitudinal wave

 Electro magnetic Theory of Light

By James Clark Maxwell

James Clark Maxwell discovered, An electro magnetic wave can propagate as transverse wave in a suitable medium at a speed of  3*10^8 m/s.

Heinrich Hertz confirmed that light is a electromagnetic wave.

This theory cannot explain Photo Electric Effect

Photo electric effect

 light rays, Ultra violet rays, Gama rays falls on certain metal surfaces emits electrons from it. It is discovered by Heinrich Hertz

Quantum theory of light

By Max Planck

 

Radiant energy is not a continuous flow of energy. Energy emitted or absorbed from a light source is in the form of small packet of energy.This packet is called Quantum. A Quantum with definite energy is called Photon

Albert Einstein gives a satisfactory explanation for Photo electric effect based on Quantum Theory

 

         Explanation: When Photons of definite energy falls on the surface of certain metals they collide with electrons present in the atom and that electrons emitted from the surface . One photon can eject one electron.As the intensity of light increases the number of photons increases. as a result more electrons knocked out from the surface of the metal

Dual nature of Light

Light is an electromagnetic wave with particle nature and wave nature at the same time

DISPERSION OF LIGHT,RAINBOW

                              DISPERSION OF LIGHT

COMPOSITE LIGHT

Any light composed of two or more colours is called a composite light

DISPERSION OF LIGHT

Splitting up of a composite light in to its component colours is called Dispersion of light

NEWTON'S EXPERIMENT

 Allow sunlight (To make a narrow beam of light use a mirror and slit)  to fall obliquely on the face of a triangular glass prism.

On the other side we can observe seven colours.Violet colour seems near the base of prism.ie violet deviates more and Red deviate less. From this we can conclude sunlight consist if seven colours. So it is a composite light.

What are the colours formed on the wall?

Violet, Indigo, Blue,Green, Yellow ,Orange ,Red (VIBGYOR). The orderly arrangement of these colours is called Spectrum

Colour                     wave length(nm)

Violet                        400-440

Indigo                       440-460

Blue                          460-500

green                         500-570

yellow                        570-590

orange                       590-620

red                             620-700 

Is there any connection between wavelength and deviation of constituent colours?explain

Yes, When composite light enter from air to prism(glass) there refraction take place.When light emerge out to air from glass there is another refraction take place .According to change in wave length refraction take place at different rates.. According to the difference in wavelength the rate of deviation varies in each colour. The colour with lowest wavelength deviates most. The colour with highest wavelength deviates less. 

Why the light of torch, candle appears yellow instead of white, even though it contain same spectrum of sunlight?

 The intensity of blue color is less in the light of candle and torch . So it appears in yellow. 

CAN WE RECOMBINE THE DISPERSED COLOURS IN THE WHITE LIGHT?

Yes, Arrange the two prisms as shown in figure

                                 RAINBOW

The sunlight that incident at a suitable angle at the top of a water drop undergo two refraction and one total internal reflection inside the water drop. So the white light split in to its constituent colors.

 Why Rainbow appears in Arc Shape?
The line joining the centre of the rainbow and the observsr is called line of vision.Each color of the dispersed sun light  make a definite angle with the line of vision.For an observer from earth can see only one color from a single drop. All water drops appearing in the same colour make the same angle with line of vision.

SELF INDUCTION-MUTUAL INDUCTION- TRANSFORMERS

                    

                                 SELF INDUCTION

 When an AC current flows through a solenoid (an insulated copper wire wound in the shape of a spring) a magnetic field is produced around that wire due to the variation of current in AC ,the magnetic flux around that wire also changes .By Faraday's law of Electromagnetic induction  Whenever there is a change in magnetic flux associated with a closed circuit an induced emf is produced on that wire. This phenomenon is called electromagnetic induction

What is the change in intensity of light of a lamp can be observed when a solenoid connected to AC?

 Due to self induction an emf is produced in the solenoid.This emf always oppose the applied voltage. This emf is called back emf. Due to the back emf the applied voltage decreases .So the bulb glows dimmer.

What is the intensity of light observed if we place a iron core inside the solenoid in the above figure?

The intensity of light is very less. Because the strength of magnetic flux increases when we place a iron core inside the solenoid. So Back emf increases. So it oppose applied voltage . Then the applied voltage decreases

Can we done the same experiment using DC voltage?

No, Electro magnetic induction take place in AC current only

                               MUTUAL INDUCTION

 We can produce an electric current in the second circuit utilizing the current of first circuit even if they are not in direct contact

 

Wind insulated copper wire( wire used for electric motor winding) at one end of a soft iron core and connect its ends to a cell. At the other end of the soft iron core wind another insulated copper wire. Connects its end to a Galvanometer .

OBSERVATIONS

   When the switch is ON and OFF then we can observe a deflection in galvanometer If we keep the switch on for some time there is no deflection in galvanometer

EXPLANATION

 When current flows through first coil magnetic flux is produced around that coil. The second coil is placed in the magnetic field of first one. When the magnetic flux around first coil changes then only an emf is induced on second coil. If we kept the switch on for a while there is no change in magnetic flux linked with second coil because it is DC current. So there is no deflection

When AC current is applied in fist coil. The magnetic flux produced around that wire continuously changes. The second coil is placed in that magnetic field so emf is continuously produced on second coil. This is the working principle of TRANSFORMER

                       TRANSFORMER

 

It is an electronic device to  increase of decrease a given AC voltage. It works in the principle of mutual induction

 There are two types of transformers STEP UP and STEP DOWN

 

               STEP UP TRANSFORMER

Used to  raise a low AC voltage to high AC voltage

Number of turns in secondary coil is greater than that of primary

Thick wire is used in primary coil and thin wire is used in secondary coil

STEP DOWN TRANSFORMER

Used to  decrease high AC voltage to low AC voltage

Number of turns in primary coil is greater than that of secondary

Thick wire is used in secondary coil and thin wire is used in primary coil

If Np is number of turns in primary, Vp is voltage in primary. Ns is the number of turns in secondary, Vs is the voltage in secondary

Vs/Vp = Ns/Np