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S. P. Singh and S. Siddhanta
the annihilation of the photonic energy. This phenomenon is known as absorption.
The absorbed photons are either converted into heat or released as fluorescence
or phosphorescence. The absorption or attenuation of radiation is described by the
Beer-Lambert-Bouguer law, according to which the transmitted radiation is directly
proportional to the incident radiation I and the distance over which the absorption is
occurring. It can be represented as
d I = −μI dx
Here μ is proportionality factor or the absorption coefficient, and dI is the decline
of radiation over a distance dx. This equation leads to the Beer-Lambert or the
Beer-Lambert-Bouguer law which is expressed as
I (x) = I 0 e
−μx
In terms of classical physics, the motion of the charged particle in an electromagnetic field is subjected to Lorentz force, F
F = q(E + v × B)
where q and v are the charge and the velocity of the particle, respectively. Light
interacts mainly with the electrons, as the interaction with the nucleus is ignored due
to its higher mass. The motion due to the Lorentz force on the protons and electrons
is considered. In the case of x < <λ, the corresponding equation can be written as
follows
m
d
2 x
dt 2 = q E(x, t) + F b (x)
This equation is similar to the system where the electron acts as an oscillator
bound to an atom like a spring and is called the Lorentzian electron oscillator model.
In contrast to absorption, scattering is a type of interaction when there is little or no
loss in the energy when the photons interact with the electrons, atoms, or molecules.
Scattering can be segregated into three major types, Rayleigh, Mie, and Raman. The
general characteristics of scattering involved absorption and immediate re-emission
of the light by the atoms or molecules, and the scattered light can have any direction.
However, there can be a distribution of the cone of preferential direction, which can
be deduced from certain rules concerning the wavelength and the cross-section of
the interaction. The scattering cross-section for refractive index near to unity is given
by:
σ R =
8π
3
3
n
2
− 1
2
λ 4 N 2
S. P. Singh and S. Siddhanta
the annihilation of the photonic energy. This phenomenon is known as absorption.
The absorbed photons are either converted into heat or released as fluorescence
or phosphorescence. The absorption or attenuation of radiation is described by the
Beer-Lambert-Bouguer law, according to which the transmitted radiation is directly
proportional to the incident radiation I and the distance over which the absorption is
occurring. It can be represented as
d I = −μI dx
Here μ is proportionality factor or the absorption coefficient, and dI is the decline
of radiation over a distance dx. This equation leads to the Beer-Lambert or the
Beer-Lambert-Bouguer law which is expressed as
I (x) = I 0 e
−μx
In terms of classical physics, the motion of the charged particle in an electromagnetic field is subjected to Lorentz force, F
F = q(E + v × B)
where q and v are the charge and the velocity of the particle, respectively. Light
interacts mainly with the electrons, as the interaction with the nucleus is ignored due
to its higher mass. The motion due to the Lorentz force on the protons and electrons
is considered. In the case of x < <λ, the corresponding equation can be written as
follows
m
d
2 x
dt 2 = q E(x, t) + F b (x)
This equation is similar to the system where the electron acts as an oscillator
bound to an atom like a spring and is called the Lorentzian electron oscillator model.
In contrast to absorption, scattering is a type of interaction when there is little or no
loss in the energy when the photons interact with the electrons, atoms, or molecules.
Scattering can be segregated into three major types, Rayleigh, Mie, and Raman. The
general characteristics of scattering involved absorption and immediate re-emission
of the light by the atoms or molecules, and the scattered light can have any direction.
However, there can be a distribution of the cone of preferential direction, which can
be deduced from certain rules concerning the wavelength and the cross-section of
the interaction. The scattering cross-section for refractive index near to unity is given
by:
σ R =
8π
3
3
n
2
− 1
2
λ 4 N 2