Tag Archives: Albert Einstein

The Nature of Particles

21 Aug
Radiation Scan

Radiation Scan (Photo credit: FastLizard4)

Classical physics (Rayleigh–Jeans law, black l...

Black body radiation for T=287K, which is the ...

Black body radiation for T=287K, which is the temperature of the earth. (Photo credit: Wikipedia)

English: Black body curves of Planck for vario...

English: Black body curves of Planck for various temperatures and comparison with classical theory of Rayleigh-Jeans. Italiano: Confronto fra le curve del corpo nero della teoria di Planck e della teoria classica di Rayleigh-Jeans. (Photo credit: Wikipedia)

The nature of particle.

1.Thomson concluded that those cathode rays were made up of particles.

2. Max Planck was trying to find out a model to understand the way in which a black body emits radiation.

3. Black body is perfect emitter and absorber of electromagnetic radiation.

4. He found that this was possible only if he had assumed radiations were emitted in packets.

5. Plank’s idea was not understood until Einstein, 1905 showed that black body radiation could be understood better if it was assumed that the radiation itself was quantised,  consisting of particle like packets of energy.

6.Each is referred to as photon.

Ultraviolet catastrophe:  Classical physics can predict that black body radiation based on long wavelength but not at short wavelengths, leading a disagreement that physicist calls as U.V catastrophe.

 

 Radiation Flux —Do the worked out example.

Advertisements

Light wave or particle?

21 Aug
No. Name   of Scientist Year   Place Perspective Key   ideas
1 Democritus B.C  Ancient Greece Particle theory “atoms  swarmed into the observer’s eyes”
2 Empedocles B.C Ancient Greece Wave theory “ Objects becomes visible   when touched by light rays emitted by the object”
3 Plato B.C Ancient Greece Wave theory
4 Leonardo Da Vinci 15th century Italy Wave theory “Compared the light   reflection to echo”
5 Francesco Maria Grimaldi 1665 Italy Wave theory “ Paper  published in 1665 after his death “ worked   on diffraction supporting  La Da Vinci
6 Robert Hooke  and Boyle 1665 England Wave theory “ Compared light with   water waves” explained the colours were formed on the water due to oil film
English: Validity of several theories for peri...

English: Validity of several theories for periodic water waves, according to Le Méhauté (1976). The light-blue area is the range of validity of cnoidal wave theory; light-yellow for Airy wave theory; and the dashed blue lines demarcate the required order of Stokes’ wave theory. The light-gray shading gives the range extension by numerical approximations using fifth-order stream-function theory, for high waves (H > ¼ H breaking ). (Photo credit: Wikipedia)

Light!  Wave or particle

In the end of seventeenth century saw a fierce debate about the nature of light.  Newton compared light with a stream of particles and this was accepted for reflection and refraction could be explained using this model.  He also argued that if light were waves then it would not form the sharp image of the object. (He did not realise that the light wave were too small!)

 

No. Name   of scientist Year Place Perspective Key   ideas
7  Thomas Young 1802 England Wave   theory His   double slit experiment
8 Leon   Foucault 1853 France Wave   theory His   experimental value of speed of light gave a death blow to particle theory for   it required the light to travel faster in H2O then in N2.
9 Albert   Einstein 1905 Germany Particle   theory Photo   electric effect.

The dilemma was recreated and then it was resolved only after Louis de Broglie produced his theory of wave-particle duality. He received the Nobel Prize for the world had accepted his explanation of light as being both particle and wave!

 

This new discovery gave rise to quantum mechanics.

 

 

10 Albert   Einstein 1905 Germany Particle   theory Photo   electric effect.
11 Thomson England Particle   theory Cathode   rays
12 Max   Plank 1918 Germany Quantised Radiation Black   Body Radiation
13 Louis   De Broglie 1927 France Issue resolved Crystals do show diffraction when   illuminated by electrons as confirmed independently by Davisson and Thomson.

The dilemma was recreated and then it was resolved only after Louis de Broglie produced his theory of wave-particle duality. He received the Nobel Prize for the world had accepted his explanation of light as being both particle and wave!

 

 

This new discovery gave rise to quantum mechanics.

 

 

 

 

 

 

T

 

 

 

 

Lights

Lights (Photo credit: cycloctopus)

%d bloggers like this: