Experimental problems for classical physics

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Experimental Facts which changed the way we think
In the early 20th century scientists started to believe that the physics which they were dealing with contained discrepancies in different sections when it comes to explaning noted phenomenon through experiments. Scientists where struggling to give an explanation of the facts that arose from the experiments. The following were the experiments which made scientific community to think for an alternative. Cathode Ray Experiments: What are cathode Rays? When electric current is passed through a vacuum tube with two electrodes one connected to +ve supply and other to -ve. A beam is found to travel from one to another. They are termed as Cathode Rays J.J Thompson conducted experiments on these rays and found out that the beam can be bent using eletric and magnetic fields. So he could infer that the rays which were primarily thought of as waves consists of a charge. The particles which he discovered where given the name as electrons and deduced it has a charge of "-" (negative). Nuclear Scattering Experiments: J.J Thompson conducted the Cathode Ray experiments and suggested the plum-pudding model of the atom. Scientific community became interested in the new model of the atom proposed. Different experiments were conducted to check the accuracy of the model. Most profound one was conducted by Ernest Rutherford. He conducted the experiments by firing Alpha particles(helium Nuclei) on to a gold foil to study the nature of the atom. A photo graphic plate was introduced to the opposite side to capture the details of the experiments. He found out that most of the Alpha particles came out from the other side unaffected. This surprised him. During repeated experiments he found out that there was a spot on the plate where it seems that the Alpha particles are scattered away from the screen. This made him to realize that most of the part of the atom must be empty with a dense nucleus with a positive charge"+" with electrons enough to neutralize the charge. This paved way for the new model of atom to be proposed. The Bhor model of atom was proposed, showing the -ve charged electrons orbiting the +ve charged nucleus in a circle as the planets revolve around sun Atomic Spectral Lines, Scattering Experiments Many scientists were conducting experiments on spectral distribution of light from atomic lamps, what puzzled them the most are the spectral lines which were observed during these experiments. They found out that the spectra formed were of sharp discrete lines rather than of a continuous spectra. The line spectra which were obtained were a discrepancy when compared with the known model of atom, ie., the electron orbiting the nucleus in a circular way. Now say if the electrons are orbiting the nucleus in an atom. Any particle will absorb energy when it is excited. So the electrons which are rotating should also absorb energy, which inturn should speed up the electrons, there by reducing the orbit size. So eventually the electrons should come down crashing to the nucleus anhilating the atom. Which is not observed. This made scientific community to think of an alternative to the accepted model(The Bhor Model). Photo Electric Effect This is a phenomenon observed with light falls on certain metals and compounds. The experiments initially were conducted on an arrangement similar to the Cathode Ray experiment. Here neither cathode nor anode is heated. Instead it is observed that when certain wavelength of light falls on the cathode, electron is emited and travels to the anode thus producing an electric current. This current produced varied on the intensity of light, the amount of the amount of the barrier voltage (barrier voltage is the opposing voltage given to the anode and cathode). There is a limit to the barrier voltage above which there wont be any photo electric effect known as the stopping voltage or the Threshold voltage. The stopping voltage varied with the material used for the cathode changed, the intensity of the current measured depended on the intensity of light used, when the wave length of the light decreased the stopping voltage increased. More over as intensity is decreased the current emited also decreased. All these created confusion among the scientific community. Now say if the light was a wave there must be a time lag for the emission of the current from the time the light is shown, which was no there. In 1905 Sir Albert Einstein came out with a perfect explanation using the Quantum Hypothesis which was proposed by Max Plank. Thus giving the perfect example to the phenomenon. These all precipated the outcome of the great theory of the century The Quantum Theory. Now this theory is applied to many fields of science from engineering to chemistry. Back to basics. Hosted by www.Geocities.ws

Experimental Facts which changed the way we think

In the early 20th century scientists started to believe that the physics which they were dealing with contained discrepancies in different sections when it comes to explaning noted phenomenon through experiments. Scientists where struggling to give an explanation of the facts that arose from the experiments. The following were the experiments which made scientific community to think for an alternative.

Cathode Ray Experiments:

What are cathode Rays?

When electric current is passed through a vacuum tube with two electrodes one connected to +ve supply and other to -ve. A beam is found to travel from one to another. They are termed as Cathode Rays J.J Thompson conducted experiments on these rays and found out that the beam can be bent using eletric and magnetic fields. So he could infer that the rays which were primarily thought of as waves consists of a charge. The particles which he discovered where given the name as electrons and deduced it has a charge of "-" (negative).

Nuclear Scattering Experiments:

J.J Thompson conducted the Cathode Ray experiments and suggested the plum-pudding model of the atom. Scientific community became interested in the new model of the atom proposed. Different experiments were conducted to check the accuracy of the model. Most profound one was conducted by Ernest Rutherford. He conducted the experiments by firing Alpha particles(helium Nuclei) on to a gold foil to study the nature of the atom. A photo graphic plate was introduced to the opposite side to capture the details of the experiments. He found out that most of the Alpha particles came out from the other side unaffected. This surprised him. During repeated experiments he found out that there was a spot on the plate where it seems that the Alpha particles are scattered away from the screen. This made him to realize that most of the part of the atom must be empty with a dense nucleus with a positive charge"+" with electrons enough to neutralize the charge. This paved way for the new model of atom to be proposed. The Bhor model of atom was proposed, showing the -ve charged electrons orbiting the +ve charged nucleus in a circle as the planets revolve around sun

Atomic Spectral Lines, Scattering Experiments

Many scientists were conducting experiments on spectral distribution of light from atomic lamps, what puzzled them the most are the spectral lines which were observed during these experiments. They found out that the spectra formed were of sharp discrete lines rather than of a continuous spectra. The line spectra which were obtained were a discrepancy when compared with the known model of atom, ie., the electron orbiting the nucleus in a circular way. Now say if the electrons are orbiting the nucleus in an atom. Any particle will absorb energy when it is excited. So the electrons which are rotating should also absorb energy, which inturn should speed up the electrons, there by reducing the orbit size. So eventually the electrons should come down crashing to the nucleus anhilating the atom. Which is not observed. This made scientific community to think of an alternative to the accepted model(The Bhor Model).

Photo Electric Effect

This is a phenomenon observed with light falls on certain metals and compounds. The experiments initially were conducted on an arrangement similar to the Cathode Ray experiment. Here neither cathode nor anode is heated. Instead it is observed that when certain wavelength of light falls on the cathode, electron is emited and travels to the anode thus producing an electric current. This current produced varied on the intensity of light, the amount of the amount of the barrier voltage (barrier voltage is the opposing voltage given to the anode and cathode). There is a limit to the barrier voltage above which there wont be any photo electric effect known as the stopping voltage or the Threshold voltage. The stopping voltage varied with the material used for the cathode changed, the intensity of the current measured depended on the intensity of light used, when the wave length of the light decreased the stopping voltage increased. More over as intensity is decreased the current emited also decreased. All these created confusion among the scientific community. Now say if the light was a wave there must be a time lag for the emission of the current from the time the light is shown, which was no there. In 1905 Sir Albert Einstein came out with a perfect explanation using the Quantum Hypothesis which was proposed by Max Plank. Thus giving the perfect example to the phenomenon.

These all precipated the outcome of the great theory of the century The Quantum Theory. Now this theory is applied to many fields of science from engineering to chemistry.

Back to basics.

Hosted by www.Geocities.ws