Eelectromagnetic Wave Reflection, Refraction Diffraction at High and Low Frequency

 

  We read in books that electromagnetic wave is reflected, refracted and diffracted when strike to physical objects. A question arise in mind that why this wave behaves like this ?

 

  The more and more thorough studies of EM waves will explain the mysteries behind strange behavior of them. Like all phenomenon of EM wave the reflection, refraction and diffraction also can't explained by assuming light as only particle or only wave, here also dual nature of matter will come into account.

 

  We can assume light as waves at lower frequency and one must have to assume light as particle at higher frequency.

 

  So now firstly we can explain these phenomenon at lower frequency from Radio waves to Microwave by taking EM waves as Wave nature. The explanation for these is as follows:

1. Reflection: Reflection is occur when an EM wave hit any surface then the Electric and Magnetic field present in the wave tries to move charge particle according to them i.e. electron experience force according to wave changing it's magnitude with time. When wave get enough electron motion trapped in motion with it, that is resonance condition between wave frequency and electron circular motion. So when electrons are intended to move then they absorbs energy from wave and become unstable, so they re-emits that energy. And because the electrons are moving with same frequency and phase as the incident wave the re-emited wave has the same frequency and phase. That is the reason behind all the metal reflect a large band of EM wave because they have a much higher no. of free electrons due to metallic bonds. So those material which have greater conductivity reflects more broad band of EM spectrum.

2. Refraction: When EM wave is incident on a material such that it have more high frequency or high angular velocity that the materials electron can't move at such a high rate then the wave energy is not absorbed by the electron motion and ray is pass through the matter. But due to presence of tightly bond electrons they absorbs a little energy and re-emits immediately thus a delay factor is introduce in the wave path. So it will slow down the wave passing through the substance, and so the ray will bent by a factor what is called Refractive index.

3. Diffraction: When EM wave is incident on a sharp edge of any substance then some part of wave is stopped by the substance and other is moving with the velocity of light. Hence the light will bent at the sharp edge of any substance. The stopped energy of EM wave is trapped in electron motion thus they re-emit the energy as a light source in all the direction this is called Diffraction.

  But these explanation will fail when we extremely increase the frequency and thus energy of EM wave. Ultra Violet to Cosmic Rays phenomenon can be explained by quantum theory.

1. Reflection: Reflection will take place when the bonding energy Δm is equal or grater than the wave packet energy. They absorbs the wave packet and the and then re-emits them with same energy. That's why visible light blocks and reflected by the most substances but X-ray and gamma ray pass through them.

2. Refraction: When wave energy is greater than bonding energy then the wave pass through the substance. The wave will apply pressure on an atom this atom will absorbs the packet and become unstable, so it re-emits the packet in same direction as the atom absorbed it. Thus the wave slow down when moving through the substances. The delay factor is so low that the packet re-emitted before it's energy start the breaking of bonds on substances.

3. Diffraction: When a train of EM wave packet is strike onto a sharp edge then some of packet are absorbed and other go straight then due to missing mass they bend slightly inward the sharp edge. And absorbed packets are re-emitted by atoms in all the directions.

  This was the mystery of EM wave.....