Dichroism and Huygens Principle on Double refraction and wave theory - Dr.S. Gokul Raj - Lecture-4

SEMESTER-III - Core Paper-4 - OPTICS - SAR3A-Dichroism and Huygens Principle on Double refraction and wave theory - Lecture-4

Covered as per "University of Madras for B.Sc., (Physics) -2018 Syllabus" for affiliated Colleges

University of Madras (CBCS) - SEMESTER-III - Core Paper-4 – Optics – SAR3A - TAC3A

I have covered the lectures in bilingual (English & Tamil) for basic understanding
_________________________________________________________________________________________________
Double refraction & Huygen:
Huygens, Christiaan (krĭs`tyän hoi`gəns), 1629–95, Dutch mathematician and physicist; son of Constantijn Huygens.
He improved telescopic lenses and discovered (1655) a satellite of Saturn and studied the rings of Saturn.
His findings were described in is Systema Saturnium (1659).
He was the first to use the pendulum in clocks.
He developed a wave theory of light opposed to the corpuscular theory of Newton and formulated Huygens's principle, which holds that, concerning light waves, every point on a wave front is itself a source of new waves.
In 1678 he discovered the polarization of light by double refraction in calcite.
His chief work is Horologium oscillatorium (1673).

Dichroism
The property of some crystals and solutions of absorbing one of two plane-polarized components of transmitted light more strongly than the other

Huygen’s Explanation of Double Refraction
• Spherical wavelet associated with ordinary waves
• Ellipsoidal wavelet associated with extraordinary waves

Huygen’s wavefront theory
• Every point on a wave-front may be considered a source of secondary spherical wavelets
which spread out in the forward direction at the speed of light. The new wave-front is the
tangential surface to all of these secondary wavelets.

Double Refraction by a Uniaxial Crystal
• Crystalline materials can have different indices of refraction in different crystallographic directions. Crystals belonging to the hexagonal, tetragonal, or rhombohedral classes are uniaxial, in that they possess a unique optical axis, most often coincident with the crystallographic axis.
• Light traveling through such an anisotropic medium can exhibit double refraction or birefringence, in which an unpolarized incident light ray splits into two polarized rays with mutually perpendicular planes of vibration.
• The ray with its electric field vibrating perpendicular to the optical axis is called the ordinary ray, and is characterized by an index of refraction .
• The ray that vibrates parallel to the optical axis is called the extraordinary ray, with its index of refraction designated .
• The birefringence is the difference Δ, which can be positive or negative.

_________________________________________________________________________________________________

தலைவிளைவாக்கம் என்பது ஒளி பிரதிபலிப்பு, தேர்ந்தெடுக்கப்பட்ட உறிஞ்சுதல், இரட்டை ஒளிவிலகல் மற்றும் சிதறல் ஆகியவற்றால் உருவாக்கப்படலாம்.

இரட்டை ஒளிவிலகல் மூலம் தலைவிளைவாக்கம் உற்பத்தி செய்வதற்கான சில முறைகள் விரிவாக விவாதிக்கப்படுகின்றன.

நுண்ணோக்கிகளில் தேர்ந்தெடுக்கப்பட்ட உறிஞ்சுதலுக்கு மூலம் தலைவிளைவாக்கம் ஒளியை உருவாக்கும் இந்த முறை பயன்படுத்தப்பட்டது

_________________________________________________________________________________________________

For Previous Lectures in the Topics:

Optics - An introduction -Electromagnetic Waves - ஒளியியல் -ஒரு அறிமுகம்-Dr.S. Gokul Raj- Lecture-1

Optics - Polarization-Double Refraction - தளவிளைவு-இரட்டை ஒளிவிலகல் -Dr.S. Gokul Raj-Lecture-2

Polarisation and its applications-தளவிளைவு-அதன் பயன்பாடுகள் -Dr.S. Gokul Raj-Lecture-3

_________________________________________________________________________________________________
This Channel is focused on Physics at College Level for both graduate and post-graduate level and also Physics at School Level.
Recent advancements in Technology and Development will be discussed in detail.
_________________________________________________________________________________________________