PPT

1. WELCOME
TO
THE ORIGIN
OF
QUANTUM THEORY

2. Classical Physics
It mirrors the “ physical reality” of our sense
impressions, treat particles and waves as
separate components of that reality

3. In our every day experience there is nothing mysterious about the
concepts of Particle and Wave.
The physical reality we perceive has its roots in the microscopic
world of atoms , molecules, electrons and nuclei.
But
In this world there are neither particle or waves!!!!!!!!

4. Limitations of Classical Physics
• Black body Radiation curves
Wien’s explanation only at high frequency region
Rayleigh and Jeans explanation at low frequency
• Optical Spectra
• Photoelectric effect
• Specific Heat of Solids

5. Blackbody Radiation
When heated, all objects emit electromagnetic radiation whose
wavelength (and color) depends on the temperature of the object.
A relatively low-temperature object, such as a horseshoe forged
by a blacksmith, appears red, whereas a higher-temperature
object, such as the surface of the sun, appears yellow or white.

7. Graphic representation of spectral distribution of
blackbody radiation at different temperature

8. The Stefan-Boltmann’s Law is observed as the increase in the emission
amplitude with increasing temperature and the Wien’s Displacement
Law is observed as the shift to smaller wavelength with increasing
temperature.
Rayleigh and Jeans formula
Energy density, U(ν)=8πkT ν²dν/C3
As ν--˃ α, U(ν) = 0 Ultraviolet Catastrophe

9. Planck’s Quantum Hypothesis
Energy density, u(ν) dν = 8πhν3dν / c 3 (ehν/kT − 1)
 At high frequency hν ˃˃ kT
ehν/kT --˃ α u(ν) dν --˃ 0
• At low frequency hν ˂˂ kT and hν/kT ˂˂ 1
(ehν/kT − 1) =1/(1+ hν/kT -1) =kT/hν
Planck’s formula becomes U(ν)=8πkT ν²dν/C3

10. The atoms of the walls of the black body behave like tiny electromagnetic
oscillators each with a characteristic frequency of oscillation
1. An oscillator have energies, En=nhν
or
Oscillator energy is quantized
2. Oscillators can absorb or emit energy only in discrete units called quanta
ΔEn=Δnhν
With oscillator energy limited to nhν ,
The average energy per oscillator in the cavity walls is not kT
but instead
Average energy per oscillator,
Ɛ = hν/(ehν/kT − 1)

11. Thank You