Polarisation by reflection.pptx

Gives a brief explanation of the mechanism and working principle of Light's polarisation by reflection.

1. Polarisation by Reflection. Peer team teaching by Manoj Aravindh S Nawin Kumar M

2. UNIT 1: POLARIZATION AND DOUBLE REFRACTION Classification of polarization – Transverse character of light waves – Polarizer and analyzer – Malu’s law – Production of polarized light – Wire grid polarizer and the polaroid – Polarization by reflection – Polarization by double refraction – Polarization by scattering – The phenomenon of double refraction – Normal and oblique incidence – Interference of polarized light: Quarter and half wave plates – Analysis of polarized light – Optical activity 2

3. Table of Questions 🗒️❓ What is light? What is Polarisation in light? What are the methods that can be used for the polarisation of light? What is polarisation by Reflection? What is Brewster angle? What are the applications of polarisation? 3

4. Light ⁉️ What we generally refer to as “light” is more correctly known as ‘electromagnetic radiation’ (often abbreviated as EM radiation). The main characteristics of electromagnetic radiation are its frequency and wavelength (λ). EM radiation has an electric and magnetic field component which oscillates in phase perpendicular to each other and to the direction in which the radiation propagates. These two oscillating fields are often visualised as in the diagram above and are continually self-propagating. 4

5. Polarisation ⁉️ Polarization is a fundamental property of light and describes the direction in which the electric field of light oscillates. The majority of light sources, such as the sun, emit unpolarized light. Unpolarized light has vibrations at randomly oriented directions perpendicular to the direction of travel. For light to be polarized randomly oriented vibrations are removed or transformed into either a linear, circular or elliptical electromagnetic wave. 5

6. M ethods of production ⁉️ Wire grid polarizer and the polaroid. Polarization by reflection. Polarization by double refraction. Polarization by scattering. The phenomenon of double refraction. 6

7. Polarisation by Reflection ⁉️ Polarization by reflection, often referred to as Brewster's Law, is a phenomenon that occurs when light reflects off a transparent medium at a specific angle. The primary cause of polarization by reflection is the selective absorption of light vibrations. 7

8. Brewster’s Law ⁉️ When unpolarized light strikes a transparent surface at a certain angle known as the Brewster angle ( ), the reflected light becomes perfectly polarized parallel to the surface. Brewster's Law is given by the equation: where: is the Brewster angle. and are the refractive indices of the first and second media, respectively.   8

9. Mechanism 🧑‍🔧 The key mechanism behind Brewster's Law is the interaction of light waves with the surface electrons of the medium. When light strikes a surface, it induces oscillations in the electrons. The reflected light is polarized because at the Brewster angle, the component of the electric field parallel to the surface is preferentially absorbed by the surface electrons, while the perpendicular component is reflected. 9

10. Applications ⁉️ 1. Reducing Glare: Sunglasses: The lenses of many sunglasses contain a polarizing filter that blocks light with a specific polarization, significantly reducing glare from reflective surfaces like water, snow, and car windshields. Anti-Glare Screens: Laptop and phone screens with integrated polarizing filters enhance screen visibility by minimizing glare from overhead lighting and reflections.

11. Applications ⁉️ 2. Enhancing Colors and Contrast: Photography: Photographers use polarizing filters to increase the saturation of blue skies and foliage, darken water reflections, and reduce atmospheric haze. Art and Museum Displays: Polarizing filters can be applied to paintings and exhibits to reduce unwanted reflections from glass cases and enhance the vibrancy of colors .

12. Applications ⁉️ 3. Scientific and Technological Applications: Liquid Crystal Displays (LCDs): LCDs rely on the controlled manipulation of polarized light using liquid crystals to achieve color and image representation. Medical Diagnostics: Polarized light microscopy facilitates the examination of biological tissues and materials by revealing details hidden in unpolarized light.

13. Nothing in life is to be feared, it is only to be understood now is the time to understand more, so that we may fear less. ~Marie Curie 13

14. THANK YOU 🙏 14