The Control of reflectance and Transmittance of glass using External Magnetic Field and Sound Waves Through Electrical permittivity

Optical properties of matter are important in solar cells and smart windows design. The properties like reflection and transmition are very important in these applications. Therefore, this work is concerned with studying these properties using Maxwell’s equations. Using the expression of reflection and transmition coefficient useful relations were found. It was found that complete transmittance occurs when one applies a strong magnetic field. While applying an appropriate magnetic field leads to complete reflection and generation of amplified light in a direction normal to the incident one. Also, the thermal radiation can be reflected completely by applying sound wave having a certain frequency.


Introduction:
Electromagnetic wave plays an important role in human life.Light waves are important for vision and for plants.Plants transform light energy into useful chemical vital energy, which is important for human life and the life of living organisms [1].Light energy from the sun is also useful since solar cells change them into useful electric energy [2].Electromagnetic waves are also used in telecommunication widely.They are used for mobiles, internet, television sound and radios [3].Thus for the efficient performance of all these devices, it is important to know how electromagnetic waves interact with matter.This includes absorption, transmittance, reflection and refraction [4].Electromagnetic waves interact with matter through many processes like scattering, Compton Effect, photoelectric effect and pair production [5].The interaction of electromagnetic waves (e.w) with bulk matter is described by Maxwell's equations which treat e. was waves.But for the interaction of e. w with individual atoms is described by using photon theory [6,7].
Intensive research has been made to increases the efficiency of solar cells [8,9].One of the main factors that control the efficiency is the absorption, transmittion and reflection coefficients.The efficiency of the solar cell can be inc reased by decreasing reflection and transmition besides increasing absorption and increasing the efficiency of converting absorbed photons energies to electrical energy [10.11].
However, no intensive research had been made to see how to control and decrease reflection and transmittance using external effects.This is the aim of this work, where the effect of the external magnetic field and sound waves are exhibited in section 2. Section3 and 4 are devoted to discussion and conclusion.

Theoretical Model to Control Reflectance, Transmittance, and discussion:
According to electromagnetic theory the reflection coefficient Г and the transmission coefficient  are given by Г = (2)

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The Control of reflectance and… Elharam Eltahir, Faten Mohammed Where the impedances for the incident and reflection for medium 1beside transmition medium 2 are given by.
Thus the parameters that control reflection and transmition are the frequency f ( = 2), magnetic permeability μ, conductivity , and electric susceptibility .By finding a pathway to change some of these parameters, one can control reflection and transmition processes.
One of these important parameters is the electric permittivity which can be controlled by applying oscillating electric field E which is given by:  =  0  − (4) The equation of motion of the electron under the action of constant magnetic field of flux density B, beside the electric field  in ( 4) is given by.
̈=  +  Thus the electric dipole moment P is given by = (  +   )   = Real electric susceptibility   = Imaginary susceptibility Thus the real electric susceptibility is given by.
The electric permittivity is given by  =  0 (1 +   ) (8) It is clear from (7) that for extremely large external magnetic field.
Another way of controlling the electric susceptibility by applying sound vibrating waves in the direction of the vibration, to exert a force of.Thus the electric susceptibility and permittivity are gives by.
With frequency  =  0 For vibration Thus one can easily control the electric permittivity by attaching two very thin magnets to the sides of the transparent materials which are parallel to the electric prating field direction, or by applying sound waves from a source in the direction of electric field vibration as shown in Fig ( 1).Equation ( 1), ( 2) and (3) shows that the reflection and transmission properties are highly dependents on electromagnetic frequency, conductivity and electric permittivity.The reflectivity and transmition can be controlled partially by the electric permittivity.The electric permittivity itself can be