Forces

EVERY  WERE  IN THE UNIVERSE

            Force is every were in the universe. The word force know every one in the universe, they are fill also but they dose not know about ,What is a force? How it’s work? And who discover the force? So in this we study about force in short.

To know the force we take a some example likes

Ø  When any one pull or push you  can fill some external powers act on your body, these external powers  are called as force in physics .

Ø  When you hang on tree or any metal bar you just fill some power that push you fall on land, that is gravity of earth on type of force.

Ø  In our childhood we play with magnet, when we two different magnet of same side place near it’s go away from each other and when two different magnet of different side place near it’s attract to each other, it is also one type of force.

  Forces are meanly divided into two part real or pseudo forces.

Real  force :-    It is a type of force which is produce  due to interaction between two or more than two objects.  It has specific source of origin and it can be explain on the basic of fundamental force.

eg :-  The earth revolves around the sun in circular orbits.

Pseudo force  :-   It is commonly observed when we are travelling in bus or train and bus or train suddenly stop, then we feel push in forward direction. This push know as  pseudo force because there is no real force i.e one any push you but you can feel  any one push you.

Best example of this force is when any racing car moved along a curved road, then man feel  a force in the outward direction. That is away from center of the race track.  

The other thing that affect on the system in which force is acting is  frame of reference.

To understand the frame of reference we  take a one example. Consider two car driver ‘A’ and ‘B’ moving with uniform speed that is 100km/hr in opposite  direction of each other and comes to near of each other. Then driver ‘A’ and ‘B’ both  observed the speed of driver ‘B’ and ‘A’ is 200km/hr respectively, but a man stand on the side of rode is observed the speed of both the drivers are only 100km/hr. it is due to the frame of reference.

                         The Fundamental forces are three. i.e.

v Gravitational Force

v Electromagnetic force

v Nuclear Force

GRAVITATIONAL FORCE :-

When we throw the any object in upwards direction it’s falls down on the surface of earth due the attraction force between object and earth this force is called as gravitational force.

•       Newton’s discovered the this force and named by gravity.
•       This force is always attractive in nature and apply on both micro & macroscopic bodies.
•       It is applicable in entire universe.
•       On the earth it’s act downward. And act on center of mass of the body.
•       The motion of planet around sun and it self . Motion of moon and satellites around  earth is a best example of gravitational force.

ELECROMAGNETIC FORCE  :-

           The forces between electric charges in relative motion are called as electromagnetic force.

•     § The force between rest charge and the force between magnetic poles is called electrostatics and magnetic force respectively.

§  These forces are attractive or repulsive in nature.

 NUCLEAR FORCE :-

The force acting between proton and neutron to hold it in nucleus of atom and binding the electron on it’s  orbit.

v  This force is attractive in nature and it’s rang is 10^-14 meter.

Friends I hope so this is help you.

Particles is wave?

PARTICLES AS WAVE 

Particles is wave? Yes this question is true not a any joke. We are know that light have particle as well as wave nature, that like some particles have a wave nature that is see in this blog.

 You are know that Maxwell give his theory of wave called as electromagnetic wave and Einstein give his photoelectric  effect of photon i.e quanta.

In 1924, De Broglie postulated his theory that exhibit the wave nature of particle. The wave associated with particle are called as matter wave  or de Broglie waves. He used the Planck's postulate formula  p = h/wavelength  called as DE BROGLIE HYPOTHESIS

  i.e wavelength = h/p  ......where p = momentum of photon

                                                       h = Plank's constant 

and this equation used to postulate his successfully experiments.

Proof for p = h/wavelength: 

    In the time of Planck's it is proof that the energy of photon (E) = hv

    and Einstein is gives his most importance equation is  E = mc^2 

By using these equation Planck's give that,

                  hv = mc^2 

                  hv/c  mc 

       But v = c/wavelength

                   h/wavelength = mc      ....................{ mc  = momentum of photon (p) }

          therefor,  p = h/wavelength 

 For this equation Planck's get noble price.

  

 Some Experiments To Proved Wave Nature Of  Particles.

   

Thomson's Experiment:- 

                                     We are knot that diffraction is a phenomenon of wave. In 1927, G.P. Thomson perform a experiment to proved the de broglie hypothesis.

     When electrons from a heated filament are accelerated through a high potential difference. Then electron beam of sufficient  energy is passes through thin flim of polycrystalline material, the diffracted rays of pattern is observed on photographic plate. This experiment is perform in vacuum chamber. This diffraction pattern is similar to X-rays diffraction pattern but not due to secondary X- rays. So we can conclude that the diffraction pattern is produce  by the electrons. Therefor this experiment proving the de Broglie wave.

 

Davisson -Germer Experiment:-

              When filament is heated electrons are emitted they are accelerated by potential difference V volt, between anode and cathode. Some of  the electrons emerges from fine hole of anode, thus fine beam of electrons is incident normally on the nickel crystal and it's scattered in all direction. Detector measure the intensity  of scattered beam in the direction of making an angle. 

For different accelerated potential the intensity of scattered beam is recorded for different angle with incident beam of electrons.

Detector move in a circular path to measure the intensity of scattered beam.

This experiment perform in vacuum chamber.

From the graphs we observed  that,

 For V = 40 volt graph is smooth 

 For V = 44 volt graph become small spur and as per voltage increases the spur also increases but at 54 volt spur is maximum after this spur decreases as per voltage increases. 

It is shows that at 54 volt intensity of scattered beam is maximum that led to constructive interference.

Double - Slit Experiment:- 

              Previous two experiment proved the diffraction pattern in electron beam as like wave. But this experiment we are shows the interference of the beam of electrons.

             In this electron gun is used to supply the beam of electrons. They are passes from two fine slit and produce the interference pattern on photographic plate. On the screen we can see alternate maxima and minima. 

Electrons like particles have charge and mass, so we are say that these are have particle nature, but in the previous experiment we are proved that beam of electrons also exhibit  diffraction and interference, which is feature of wave. So this is conclude that de Broglie hypothesis. i.e. particles have wave nature. And this is called as WAVE - PARTICLE DUALISM. 

 

 

This is led to QUANTUM MECHANICS.

Do You Know Nature Of Light

          

NATURE OF LIGHT

     Do You Know the Nature Light? Today maybe  any one no the answer of this question.  And this   credits go’s to Sir. Newton’s, Einstein, Maxwell  and  Huygens etc.

 Lights  related theory  are  given by many of scientists, but it’s become most  popular and importance, When  Sir. Newton give it’s theory  ,which is popularly know  as Newton  Corpuscle Theory Of Light. So we stated  from this theory.

Newton’s  Corpuscle Theory Of Light:-

According to this theory  Newton say

v  Every source of light emits large number of particles is called as corpuscles and these corpuscle are perfectly  elastic , rigid and weightless.

v  Newton’s say light travel in a straight line ( which is now know as rectilinear propagation of light). To proved that Newton perform a experiment which is most popular, ( In this experiment he take a two or three card board and make hole in a center  of these boards , and  place as all boards in a straight line, in a one end he take  source of light and from other end observed by eye he observed that light is only visible when boards are in same line.)

v  He say different  corpuscles give different colours  and it’s prove by prism experiment. ( You  can also see this experiment in your  life when you are see your plastic scale in front of light you observed that those light which is passing from scale is in rembo  colours.)

v  Newton say light have particles nature.        

Newton’s got many  successes like he explain rectilinear propagation of light, reflection and refraction of light. But some drawbacks in there that is he could not explain interference, diffraction and polarization of light etc.

His theory say that speed of light in a denser medium is more than rarer medium (Which is wrong)

Hence  Newton’s Corpuscle  theory is  rejected, but some points are accepted.

After the Newton’s   Maxwell  is came with his theory called as

Electromagnetic theory of light :-

           According to this,

                          Light is a electromagnetic wave and dose required a any medium to propagation of  light. They travel even in vacuum.  He show the relation between magnetism and electricity and he found the velocity of electromagnetic  wave is equal to velocity of  light (300000km/sec) by experimentally.  ( Which is accepted  by many scientists )

 In 1678, to overcome the Newton  corpuscular theory, Huygens’ came with his theory which is popularly know  as  wave theory of light.

  Wave  Theory  Of  Light:-

            According  to this,

v  Light travel in a form of longitudinal wave with uniform velocity and it’s required  a medium. (But later on proved that light is a transverse wave and it’s dose not required any material medium.)

v  Huygens’ explain the law of reflection, refraction interference ,diffraction etc.

v  Also Huygens’ show that the velocity of light in denser medium is less than rarer medium. ( Which is Newton dose not show )

v  Huygens’ assumed that for propagation of light required a hypothetical  medium is called as ‘luminiferous  ether’  and it’s density is zero & it is perfectly transparency. ( By experimentally  proved that  it is dose not exists)

Huygens’ give it’s principle with define of Wavefront.

Wavefront :   A locus of all the points of medium to which waves reach simultaneously  so all                                 the  points are in the same phase is called wavefront.

HUYGENS’ PRINCIPLE:- Every point on a wavefront behave as secondary source of light and sending secondary wave in  all  possible direction, such that new secondary wavelets are form in a direction of propagation of wave.

          According to his theory light have wave nature.

     After this scientists society divides into two part, one which say light have particles anther which say light have wave nature.

 Then nature of light become more importance question for every one in world.

     After that the great scientists come with his theory that theory change the thought of all scientists in world about nature of light i.e Einstein's. He gives his theory called as Photoelectric Effect in 1905.

Einstein's Photoelectric Effect:-

                      According to him, Light travel in the form quantum which is called photon.

                                                  A process in which due to the energy of  incident photon (hv) surface                                                    electrons become free electrons when light incident on metal surface.

Where,  E= hv = Energy of incident photon

              h = Planck's constant 

              v  = Frequency of incident photon                                    

   

Einstein's also give Photoelectric Equation;

                                                                                         

                                                                 hv = w + 1/2 mv^2

where w = required energy

         K.E.= 1/2mv^2 = Kinetic energy

         m = mass of photon & v = velocity of photon

since. w = hv0 

therefore,  hv  =  hv0 + 1/2mv^2

                  1/2mv^2 =  h(v - v0)

    This is a photoelectric equation

For this Einstein was awarded Nobel Prize in 1921

Due these theory's it is show that light have  Dual Nature. (i.e   in photoelectric effect show light have photon and it's mass, which is in particles which is explain reflection, refraction, and rectilinear propagation of light, but only wave nature shows  interference, diffraction and polarization of light)