Chapter 9 Physics Class 11 Notes

• Important from chapter 9 physics class 11 important questions Punjab Textbook.
• Wavefronts
• Huygen's principle
• Interference of light waves
• Conditions for detectable interference
• Important from chapter 9 physics class 11 numericals Punjab Textbook.
• Young's double-slit experiment
• Interference in thin films
• Newton's rings
• Michelson interferometer
• Important from chapter 9 physics class 11 exercise solutions Punjab Textbook.
• Diffraction of light
• Diffraction due to a narrow slit
• The selective absorption method is the most common method to obtain plane polarized light by using certain types of materiais called dichroic substances. These materials transmit only those waves, whose vibrations are parallel to a particular direction and will absorb those waves whose vibrations are in other directions: One such commercial polarizing material is a polaroid.
• If un-polarized light is made incident on a sheet of polaroid, the transmitted light will be plane polarized. If a second sheet of polaroid is placed in such a way that the axes of the polaroids, shown by straight lines drawn on them, are parallel (Fig. 9.15a), the light is transmitted through the second polaroid also. If the second polaroid is slowly rotated about the beam of light, as axle of rotation, the light emerging out of the second polaroid gets dimmer and dimmer and disappears when the axes become mutually.
• Diffraction grating
• Diffraction of X-rays by crystals
• Important from chapter 9 physics class 11 exercise Punjab Textbook.
• Polarization: In transverse mechanical waves, such as produced in a stretched string, the vibrations of the particles of the medium are perpendicular to the direction of propagation of the waves. The vibration can be oriented along vertical, horizontal or any other direction (Fig. 9.13). In each of these cases, the transverse mechanical wave is said to be polarized. The plane of polarization is the plane containing the direction of vibration of the particles of the medium and the direction of propagation of the wave.
• A light wave produced by oscillating charge consists of a periodic variation of electric field vector accompanied by themagnetic field vector at right angle to each other. Ordinary light has components of vibration in all possible planes. Such a light is unpolarized. On the other hand, if the vibrations are confined only in one plane, the light is said to be polarized. Production and Detection of Plane Polarized Light.
• The light emitted by an ordinary incandescent bulb (and also by the Sun) is unpolarized, because its (electrical) vibrations are randomly oriented in space (Fig. 9.14). It is possible to obtain plane polarized beam of light from un-polarized Sight by cemoving all waves from the beam except those having vibrations along one particular direction. This can be achieved by various processes such as selective absorption, reflection from different surfaces, refraction through crystals and scattering by small particles.
• Production and detection of plane-polarized light
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• Optical rotation:  When a plane polarized light is passed through certain crystals, they rotate the plane of polarization. Quartz and sodium chlorate crystals are typical examples, which are termed as optically active crystals. A few millimeter thickness of such crystals will rotate the plane of polarization by many degrees. Certain organic substances, such as sugar and tartaric acid, show optical rotation when they are in solution. This property of optically active substances can be used to determine their concentration in the solutions.
• Important from chapter 9 physics class 11 conceptual questions Punjab Textbook.

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