Electromagnetic spectrum and the LASER

The dual nature of the light
Wave
(propagation)
• Diffraction
• Interference
• Polarization
Particle
(interaction)
• photoeffect
• Compton-effect
Albert Einstein (1905) : photoelectric effect
photon (light quantum), its energy: E = h·n (or E = h·f)
Louis-Victor de Broglie (1924) : Matter-waves theory
(All materials have wave nature as well.)
λ = h/p, where p is the impulse => λ = h/m·v
Polarization
Important physical quantities and
relations
Frequency: n (1/s)
Wavelength:
� (m)
Wavenumber: n (cm-1 )
c
v
1
�
Energy: E (J) h . n
Extinct. coeff.:� (M -1 cm -1 or (mg/ml) -1 cm -1 )
a
Interference
�x � s � s � a�
sin�
1
2
Einstein: energy of a photon (light-quantum)
To achieve max. gain: To achieve max. weakening:
1
a� sin� � n�
� a�
� � ( n � ) ��
sin 2
Linearly polarized light
2