Reflectiond And Transmition Of EM

WavesTalk by:Imane Hafnaoui

Outlines

o Introductiono Reflection o Reflection and transmission

coefficientso Types of reflectiono Polarizationo Applications

IntroductionWaves can be found in two forms.• Mechanical waves propagate through a medium, and the substance of this medium is deformed. Eg: Sound, water, ...

•Electromagnetic waves, do not require a medium. Instead, they consist of periodic oscillations in electrical and magnetic fields generated by charged particles, and can therefore travel through a vacuum.

Reflection and Transmission

Why is it so important to learn about reflection?

It is because with every existing wave, there is reflection and refraction.

Reflection is the change in direction of a wave at an interface between two different media so that the wave returns into the medium from which it was originated.

Reflection and Transmission coefficients

• Boundary conditions

Reflection and Transmission coefficients

Reflection and Transmission

Solving gives:

Reflection and TransmissionA wave is partially reflected and partially transmitted at the boundary between media in which it has different speeds.1.Inverted Wave: when the wave travels from a light medium (fast) to a heavier medium (slow), the reflected wave is inverted.

2.Un-inverted wave: the reflected wave stays the same if the incident wave travels from a heavier medium to a lighter one.

Polarization

Definition The polarization is described by

specifying the orientation of the wave's electric field at a point in space over one period of the oscillation.

Polarization

• Parallel polarization:The electric field vectors are parallel to the plane of incident.

• Perpendicular polarization:The electric field vectors are perpendicular to the plane of incident.

There are two types of linear polarization

Polarization

• Brewster’s Angle: also known as the polarizing angle where given an incident wave, there is no resulting reflection.

The magnitude of the reflection coefficient depending on the firing incident angle, for the parallel and perpendicular polarization

Total Internal Reflection

There is an angle called critical angle at which the incident wave is completely reflected.

From Snell’s Law :

Total Internal Reflection

We get,

Important application is in fiber optic cables.

Applications

• Desired reflection:- Laser- Radar - Spacial imaging- Optical sensors- Medical imaging

Applications• Undesired reflection:

– Sometimes reflection is unwanted so it is good to know about it in order to develop techniques to remove or minimize this reflection.

Example: we want to have max transmission of the incident light to go into the binoculars. Solution is to cover the lenses with a coating with specific index of refraction to minimize reflection.

Thank You