Faraday effect

How to find the verdet's constant. This presentation discovers the basic concept behind the experiment of determing the verdet's constant for different substances

1. FARADAY EFFECT

2. Aim: To determine the Verdet’s Constant of Glycerine

3. APPARATUS Electromagnets, Constant current supply, Light source, Cubes (hollow, with water and with glycerine ), Collimator, Telescope

4. THEORY OF EXPERIMENT This experiment, which is in theory similar to that of the Magneto-Optic Effect or Faraday Effect.  It is called magneto-optic phenomenon as it is, an interaction between  light  and a  magnetic field in a medium. The Faraday effect causes a rotation of the plane of polarization which is linearly proportional to the component of the magnetic field in the direction of propagation

5.  This effect occurs in most optically  transparent dielectric materials (including liquids) under the influence of magnetic fields The Faraday effect is caused by left and right circularly polarized waves propagating at slightly different speeds, a property known as circular birefringence.

6. Physical Interpretation of the Faraday effect The linear polarized light that is seen to rotate in the Faraday effect can be seen as consisting of the superposition of a right- and a left- circularly polarized beam. In circularly polarised light the direction of the electric field rotates at the frequency of the light, either clockwise or counterclockwise.

7. The electric field vectors of a traveling circularly polarized electromagnetic wave.

8. This changes the dynamics of the interaction for each beam and When the two beams are added after the phase shift, the result is again a linearly polarized beam, but with a rotation in the polarization direction. The direction of polarization rotation depends on the properties of the material through which the light is shown.

9. Image showing Polarization rotation due to the Faraday effect

10. FORMULA USED The relation between the angle of rotation of the polarization and the magnetic field in a transparent material is: Q= VBd Q is the angle of rotation (in radians), B  is the magnetic flux density in the direction of propagation (in  teslas ), d  is the length of the path (in meters) where the light and magnetic field in Interact and V is the  Verdet constant  for the material. 

11. PROCEDURE Focus the telescope for clear object image far from it. Make the experimental arrangement. Place a hollow glass cube between the pole pieces of electromagnet on wooden stand. Apply a constant current supply say 3A to the electromagnet and note the minimum intensity of slit. Say it Q1

12. 5. Now, reverse the direction of current and again note the minimum intensity say,Q2 6. Calculate Q(min) 7. Now, note the values of Q1’ and Q2’ by same method for water and find magnetic field 8. Now, replace the cube containing water with Glycerine and find the Verdet’s constant.

13. APPLICATIONS The Faraday effect has been used to measure optical rotatory power and for remote sensing of magnetic fields (such as fiber optic current sensors ). The Faraday effect is used in  spintronics research to study the polarization of electron spins in semiconductors.  Faraday rotators can be used for amplitude modulation of light, Faraday rotator are the basis of optical isolators and optical circulators such components are required in optical telecommunications and other laser applications.