FSc ICS Notes Physics XI Short Questions & Definitions Chapter 9 Physical Optics 1st Year Physics Notes Online Taleem Ilm Hub
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Optics: Branch of Physics which deals with the study of the behaviour of light.
Physical optics: It treats the distinctive wave phenomena of light.
Light: The aspect of radiant energy of which an observer is visually aware.
Luminous: Objects that give off light of their own.
Interference: The phenomenon in which the two waves support each other at some points and cancel at others.
Vibration: One complete round trip of the body.
Concentric: Having a common center, as circles.
Wave front: i) A surface on which all the points have the same phase of vibration. ii) Locus of all points having the same phase of vibration.
Phase: The state or condition as regards its position and direction of motion with respect to the mean position.
Ray: A single line of light coming from a luminous point.
Luminous: Objects that give off light of their own.
Beam: Several parallel rays of light considered collectively.
Spherical (circular) wave front: In homogeneous medium, from a point source, concentric spheres (circles) of wave fronts with center at the source.
Plane wave front: A small portion of a spherical wave front which is very nearly plane.
Huygen’s principle: Every point on a wave front can be considered as a source of secondary spherical wave-lets, and the new position of the wave front after a time t can be found by drawing a plane tangential to the secondary wave-lets.
Tangent: A line, curve, or surface which touches another at a single point.
Diffraction: The bending or spreading of waves around the edge of an opening or obstacle.
Phase: The state or condition as regards its position and direction of motion with respect to the mean position.
Constructive interference: The interference of two waves, so that they reinforce one another.
Destructive interference: The interference of two waves, so that they cancel one another.
Phase coherence: Producing of two waves of same wavelength and time period at the same instant.
Monochromatic: Light consisting of only one colour.
Polychromatic: Light composed of several colours.
Coherent source: Having a source or sources, that are always in phase, i.e. peaks and troughs always come together.
Superposition: Combining the displacements of two or more wave motions algebraically to produce a resultant wave motion.
Fringe: One of various light or dark bands produced by the interference or diffraction of light.
Crest: A region of upward displacement in a transverse wave.
Trough: A region of downward displacement in a transverse wave.
Maxima: The bright fringes made in the interference of light.
Minima: The dark fringes made in the interference of light.
Slit: A narrow opening; to cut lengthwise or into long strips.
Integral multiple: Multiples having a whole number.
White light: Light such as daylight, containing all wavelengths of the visible spectrum at normal intensities so that no coloration is apparent.
Thin film: A thin skin or layer.
Plano-convex lens: A convex lens whose one side is plane.
Refraction: The bending of a wave disturbance at it passes obliquely from one medium into another of different density.
Periphery: The circumference of a circle, ellipse, or similar figure; the outside surface of a rounded solid.
Microscope: An optical instrument for producing an enlarged image of small objects.
Simple microscope: The magnifying glass, or simple magnifier. The small object is viewed between the lens and its focal point.
Compound microscope: A device used for producing large images of close small objects with a combination of lenses.
Concentric rings: Rings having a common center.
Newton’s rings: Circular interference fringes formed between a lens and a glass plate with which the lens is in contact.
Michelson’s interferometer: The device includes one half silvered mirror and two plane mirrors, using interference of light waves to measure very small distances.
Precision: In measurements considering the magnitude of error. The less magnitude of error gives more precise measurement.
Telescope: A device for collecting and producing an image of distant objects.
Cadmium: ( 48Cd112 ) A soft bluish metal, used in low-melting point alloys to make solders in some batteries.
Rim: A border, edge, or margin of an object, especially when bound or raised.
Diffraction: i) The property of bending of light around obstacles and spreading of light waves into the geometrical shadow of an obstacle. ii) The bending or spreading of waves around the edge of an opening or obstacle.
Diffraction grating: An optical surface, either transmitting or reflecting with several thousand equally spaced and parallel lines ruled on it.
Grating element: Distance of the width of slit and the separation between two consecutive slits, which is equal to length of grating divided by number of ruled lines.
X-rays: Electromagnetic radiation of extremely short wave length, having great penetrating power.
Crystal: A (usually transparent) body formed by a substance solidifying so that it has flat surfaces in regular, even arrangement.
Electromagnetic radiation: Energy propagated by vibrating electric and magnetic fields. Electromagnetic radiation forms a whole electromagnetic spectrum, depending upon frequency and ranging from high frequency cosmic rays to low frequency microwaves.
Array: An orderly collection or series of things imposingly displayed.
Bragg equation: The equation setting out the condition for the diffraction of a parallel beam of monochromatic x-rays from a crystal; n λ = 2 d sin θ
Biology: The science, which deals with the origin and life history of plants and animals including botany and zoology.
Biological: Pertaining to the science, which deals with the origin and life history of plants and animals including botany and zoology.
Hemoglobin: Hemoglobin is a protein that is carried by red cells. It picks up oxygen in the lungs and delivers it to the peripheral tissues to maintain the life of cells.
Helix: Anything in the shape of the thread of a screw, or of a coiled spring.
Analyzer: A device for determining the plane of polarization of plane-polarized radiation.
DNA: (Deoxyribonucleic acid) The genetic material of most living organisms, which is a major constituent of the chromosomes within the cell nucleus and plays a central role in the determination of hereditary characteristics by controlling protein synthesis in cells.
Transverse mechanical waves (or Transverse waves): The waves in which particles of the medium are displaced in a direction perpendicular to the direction of propagation of waves.
Electric field: The region in which an electric force acts on a charge brought into the region.
Electric field vector: The vector area in which an electric force acts on a charge brought into the region.
Magnetic field: The region or space near a magnet where the effects of magnetism such as the deflection of compass needle can be detected.
Magnetic field vector: The vector area near a magnet where the effects of magnetism such as the deflection of compass needle can be detected.
Polarization (of light): The limiting of the vibrations of light, usually to vibrations in one plane.
Plane polarized light: A beam of light in which all the vibrations are in one direction.
Polarizer: Crystal which stop light vibrations in all but one direction.
Polaroid filter: A light filter which polarizes the light passing through it.
Optical activity: The property of rotating the plane of polarization of light.
Incandescent: Glowing with heat; white-hot.
Absorption: In radiation. Reduction in the intensity of electromagnetic radiation, or other ionizing radiation, on passage through a medium.
Reflection: The turning back of a wave from the boundary of a medium.
Scattering: The spreading out of a beam of radiation as it passes through matter, reducing the energy moving in the original direction.
Dichroism: The property of some crystals, such as tourmaline, of selectively absorbing light vibrations in one plane while allowing light vibrations at right angles to this plane to pass through.
Dichroic substances: The property of some substances (or crystals), such as tourmaline, of selectively absorbing light vibrations in one plane while allowing light vibrations at right angles to this plane to pass through.
Polaroid: A doubly refracting material that plane-polarizes unpolarized light passed through it.
Crystal: A (usually transparent) body formed by a substance solidifying so that it has flat surfaces in regular, even arrangement.
Amorphous: Describing a solid that is not crystalline; i.e. one that has no long-range order in its lattice.
Quartz: (SiO2) The most abundant and common mineral, consisting of crystalline silica, crystallizing in the trigonal system.
Sodium chlorate: (NaClO3 ) A white crystalline solid. It decomposes above its melting point to give oxygen and sodium chloride.
Optically active crystal: The property possessed by some crystals of rotating the plane of vibration of polarized light passing through it.
Organic chemistry: The branch of chemistry concerned with compounds of carbon.
Organic substance: A substance containing carbon compounds; vegetable and animal origin substances.
Sugar: Any of a group of water-soluble carbohydrates of relatively low molecular weight and typically having a sweet taste.
Tartaric acid: [(CHOH)2 (COOH)2 ] A crystalline naturally occurring carboxylic acid.
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