In this article we will discuss Specific distribution in black body radiations. It includes experimental results as well as graphical representation.
Lummer & Pringsheim investigated the distribution of energy among the radiation emitted by black body at different temperatures.The experimental arrangement of Lummer & Pringsheim is shown in the figure below :
• The radiation from the black body passes through the slit S1 and falls on reflector M1. The parellel beam of radiation falls on rock-salt or fluorspar prism ABC placed on the turn table of spectrometer after the reflection.
• The emergent light is focused by the reflector (concave mirror) M2 on a line bolometer placed behind the slit S2 .The bolometer is connected to a sensitive galvanometer.
• The turn table is rotated slowly so that different part of radiation spectrum successively falls on the bolometer & corresponding deflections in galvanometer connected in bolometer circuit are read.
The intensity of each line is proportional to deflection in galvanometer.
Then a curve is drawn between intensity & wavelength. The distribution curves drawn for different temperatures are shown below :
The curve shows that the :
i) The distribution of energy is not uniform in the radiation spectra of a black body.
ii) At a given temperature, the intensity of incident radiation increases with increases of wavelength and become maximum at particular wavelength.
iii) An increase in temperature cause a decrease in λm such that :
λm.T = constant = 0.2896
where, λm = wavelength for which energy emitted is maximum.
T = Temperature
This relation is called Weins displacement law.
iv) An increase in temperature causes an increase in energy emission for all wavelength.
v) The area under which curve represent the total energy emitted by the body at a particular temperature for a range of wavelength considered.
This area increases with increase of temperature. That area is directly proportional to fourth power of absolute temperature.
E ∝ T4
This is known as Stefan’s law.
In this article we are going to discuss Inadequacy of classical mechanics and origin of quantum mechanics. So let us start with the basis of development of classical mechanics.
The development of Classical mechanics is based on Newton’s three laws :
- Law of Inertia
- Law of Force
- Law of Action and Reaction
The classical mechanics explain correctly the motion of celestial body like planets, stars, and microscopic terrestrial body moving with non- relativistic speed.
Inadequacy of Classical Mechanics are :
- It does not holds in region of atomic dimensions.
- It could not explain the observed spectra of black body radiation.
- It could not explain the observed variation of specific heat of metal and gases.
- It could not explain observed spectrum of black body radiation.
- It could not explain the origin of discrete spectra of atoms since according to classical mechanics the energy changes are always continuous.
- Classical Mechanics could not explain the large number of phenomenon like photoelectric effect, Raman effect etc.
The inadequacy of Classical Mechanics led to origin of Quantum Mechanics.
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