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Polarization 1, polarization of light, physical optics
- 1. Light Prepared By: Ms. Sumaira Ghafoor
- 2. Briefly • In physics, the term light sometimes refers to electromagnetic radiation of any wavelength, whether visible or not. • Primary properties of light are intensity, propagation direction, frequency or wavelength spectrum, and polarization. • Its speed in a vacuum, 299,792,458 meters per second, is one of the fundamental constants of nature. • The study of light, and the interaction of light and matter is termed optics, is an important research area in modern physics.
- 3. • Light, which is emitted and absorbed in tiny "packets" called photons, exhibits properties of both waves and particles. This property is referred to as the wave–particle duality.
- 4. End of visual rays “There is no vision unless something comes from the visible object to the eye, whether or not anything goes out” camera obscura Alhazen (Ibn al-Haytham) Born July 1, 965 CE (354 AH) Basra in present-day Iraq, Buyid Persia Died March 6, 1040 (aged 74) (430 AH) Cairo, Egypt, Fatimid Caliphate Fields physicist and Mathematician Known for Book of Optics, Doubts Concerning Ptolemy, On the Configuration of the World, The Model of the Motions, Treatise on Light, Treatise on Place, scientific method, experimental science, experimental physics, experimental psychology, visual perception, analytic geometry, non-Ptolemaic astronomy, celestial mechanics Influences Aristotle, Euclid, Ptolemy Influenced Averroes, Witelo, Roger Bacon, Kepler Over-confident about practical application of his mathematical knowledge, he assumed that he could regulate the floods of the Nile.
- 5. Michelson's method was to shine a light on the rotating hexagonal mirror, which then reflected to the other mirror 35 kilometres away. The mirror needed to make one-eighth of a rotation in the time it took the light to make the return trip. This meant that the octagonal mirror had to be turning at about 32 000 rpm. From the round trip distance the light travelled, and the period of rotation of the octagonal mirror, the speed of light was determined quite accurately. Albert Abraham Michelson Born December 19, 1852; Strzelno, Kingdom of Prussia Died May 9, 1931; Pasadena, California United States; Physics Alma mater: United States Naval Academy, University of Berlin; Doctoral advisor: Hermann Helmholtz; Doctoral students: Robert Millikan Known For Speed of light Michelson-Morley experiment Notable awards Nobel Prize for Physics (1907) Copley Medal (1907) Henry Draper Medal (1916)
- 6. Transverse Waves • Energy is perpendicular to direction of motion • Moving photon creates electric & magnetic field –Light has BOTH Electric & Magnetic fields at right angles!
- 7. 7 Visible Light • We now know what we see is part of the electromagnetic spectrum. We know that the light waves enter our eye, and stimulate parts of it that cause a electrical impulse to be sent to the brain which creates this visual image. • But everything does not emit radiation. How do we see those things? And why cant we see a window?
- 8. Seeing colour • The colour an object appears depends on the colours of light it reflects. For example, a red book only reflects red light: White light Only red light is reflected
- 9. A white hat would reflect all seven colours: A pair of purple trousers would reflect purple light (and red and blue, as purple is made up of red and blue): Purple light White light
- 10. Using coloured light • If we look at a coloured object in coloured light we see something different. For example, consider a football kit: White light Shorts look blue Shirt looks red
- 11. • In different colours of light this kit would look different: Red light Shirt looks red Shorts look black Blue light Shirt looks black Shorts look blue
- 12. Seeing things • We know that when waves run into a boundary they are partially transmitted and partially reflected. • Light behaves as a wave, so it to is reflected. • Therefore, an object does not need to emit photons itself to be seen, it just has to reflect light back to our eyes where we can detect it. • Objects that do not allow light to pass through them are called opaque. • Objects that allow light to pass through them are considered transparent. • Objects in between are called translucent.
- 14. Wave Theory – Light travels as a transverse electromagnetic wave
- 15. POLARIZATION… • Light is an electromagnetic wave. • EM waves are those waves in which there are sinusoidal variation of electric and magnetic fields at right angles to each other as well as to the direction of propagation of wave.
- 16. POLARIZATION… The light which acquired the property of one-sidedness (Direction of vibration) is called polarized light. The un-polarized light consists of an infinite number of waves, each having its own direction of vibration.
- 17. POLARIZATION… From Sun, bulbs, candles No fixed plane of oscillation Random changes in direction of light Filtered Light Fixed plane of oscillation Half of the intensity of unpolarized light
- 18. POLARIZATION… Polarized light has it E field in one direction. Light is normally un-polarized. – Selective Absorption – Polaroid filter – Reflection through surfaces – Brewster’s angle _ Refraction through crystals – Scattering by small particles– Light from the sky Polarized light has many applications – Polaroid sunglasses, Polarization microscopy, liquid crystal display.
- 19. POLARIZATION…
- 20. POLARIZATION… Filters to transform un-polarized light to polarized light Polaroid filter Enables only 1 polarization of light to pass through.
- 21. POLARIZATION… 21
- 22. POLARIZATION… 22
- 24. POLARIZATION… 24 Malus' law. When a perfect polarizer is placed in a polarized beam of light, the intensity I of the light that passes through is given by equation I=I0cos2θ, where θ is the angle between the light's initial polarization direction and the axis of the polarizer.
- 25. POLARIZATION…
- 26. POLARIZATION…
- 30. POLARIZATION… 30 Pictorial polarized light Vertically Polarized light (п – vibration) Horizontally Polarized light (σ – vibration) . . . .. ... . . .. .. .. Un Polarized light (п & σ – vibration)
- 31. POLARIZATION… Plane of vibration and Plane of polarisati
- 32. POLARIZATION… • a) horizontally • b) vertically horizontalvertical direction of polarization of reflected light
- 33. POLARIZATION… wearing sunglasses will help reducing glare (reflection) from flat surfaces (highway/water) without with sunglasses
- 35. POLARIZATION… 35 Liquid Crystal (LCD) Displays Stress Analysis
Editor's Notes
- Photographic Filters When light reflects off water it becomes polarised. Such light is often called glare and can make it harder to see what's behind it. Photographers often use filters to cut out glare and get better pictures. Liquid Crystal (LCD) Displays There are some crystals that become aligned when an electric field is put across them. When this happens they act as polarising filters. The thicker the material the more it is rotated and different colours are rotated by different amounts.
- Photographic Filters When light reflects off water it becomes polarised. Such light is often called glare and can make it harder to see what's behind it. Photographers often use filters to cut out glare and get better pictures. Liquid Crystal (LCD) Displays There are some crystals that become aligned when an electric field is put across them. When this happens they act as polarising filters. The thicker the material the more it is rotated and different colours are rotated by different amounts.