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PhysicsSubject :Ray optics: Optical

InstrumentsPHYSICS

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I'd like to express my greatest gratitude to the people who have helped & supported me throughout my project. I will treasure the knowledge imparted to me by Mr. M.Bagdi, my grateful thanks to him for the able teaching and guidance, his continuous support for the project, from initial advice & encouragement to this day. I thank Mr. Chotelal, the Lab assistant for his cooperation.

Special thanks of mine goes to my colleague who helped me in completing the project by giving interesting ideas, thoughts & made this project easy and accurate.

I wish to thanks OUR SCHOOL PRINCIPAL MRS. KIRAN AWASTHI forher_constant_support. .

I wish to thanks my parents for their undivided support & interestwho inspired me & encouraged me to go my own way, without which I would beunable to complete my project.

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Acknowledgement

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KendriyaVidyalayaMhow

I certify that Mas.Akshay Kumarof class XII ‘A’worked on the project “Ray Optics:OpticalInstuments” under my super vision. He has completed his work successfully during the session 2012-13 .

This project is considered as fulfillments of the AISSCEExamination conducted by CBSE, New Delhi.

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Certificate

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Certificate(Page No. Certification)

This is certify that this Physics Investigatory Project work is the soul propertyof Akshay Kumar

Guptacontaining32pages……….

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Content1. Acknowledgement2. Certificate3. Declaration4. Introduction to Ray Optics5. Content6. Ray Optics

a. the human eyei) Introduction to human eyeii) Working of the eyeiii) Defects of vision

b. The Camera c. The Microscope

i) Simple microscopeii) Compound microscope

d. The Telescope

i) Refracting type telescopeii) Reflecting type telescope

e. Early telescopesf. Telescopes of the worldg. Hubble Space Telescope

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h. Chandra X-Ray Telescopei. Breaking News (Latest information)

7.Biplography

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Introduction to Ray optics

Optics, branch of physical science dealing with the

propagation and behavior of light. In a general sense, light is that part of the electromagnetic spectrum that extends from X rays to microwaves and includes the radiant energy that produces the sensation of vision (ElectromagneticRadiation , Energy; Spectrum, X Ray). The study of optics is divided into geometrical optics and physical optics, and out of these branches Geometrical Optics or Ray Opticsare discussed below.

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The Ray Optics ,uses the geometry of straight lines to accountfor macroscopic phenomenon like rectilinear propagation ,reflection ,refraction ,etc. That is why Ray Optics is called Geometrical Optics.

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Optical Instruments

Optical instruments are the devices which help human eye

i) in observing highly magnified images of tiny objects ,for detailed examination,eg.Microscope,

ii) ii) in observing very far off objects-terrestial or astronomical, eg. Telescope.

The essential optical component in making these instruments are convex and concave, lens and mirrors.

The images are formed by refraction through lenses and byreflection through mirrors.

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TheHuman Eye

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Fig. Close up photograph of cornea of the human-eye

The entire eye, often called the eyeball, is a spherical structure approximately 2.5 cm (about 1 in) in diameter with a pronounced bulge on its forward surface. The outer part of the eye is composed of three layers of tissue. The outside layer is the sclera, a protective coating. It covers about five-sixths of the surface of the eye. At the front of the eyeball, it is continuous with the bulging, transparent cornea. The middle layer of the coating of the eye is the choroid, a vascular layer lining the posterior three-fifths of the eyeball. The choroid is continuous withthe ciliary body and with the iris, which lies at the front of the eye. The innermost layer is the light-sensitive retina.

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• Working of the Eye

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Light entering the eye passes through a transparent structure called the cornea, behind which are a clear liquid (the aqueous humor), a variable aperture (the pupil, which is an opening in the iris), and the crystalline lens. Most of the refraction occurs at the outer surface of the eye, where the cornea is covered with a film of tears. Relatively little refraction occurs in the crystalline lens because the aqueous humor in contact with the lens has an average index of refraction close to that of the lens. The iris, which is the colored portion of the eye, is a muscular diaphragm that controls pupil size. The iris regulates the amount of light entering the eye by dilating the pupil in low-light conditions and contracting the pupil in high-light conditions.The f-number range of the eye is from about f/2.8 to f/16.

The cornea–lens system focuses light onto the back surface of the eye, the retina, which consists of millions of sensitive receptors called rods and cones. When stimulated by light, these receptors send impulses via the optic nerve to the brain,where an image is perceived. By this process, a distinct image of an object is observed when the image falls on the retina.

• Defects Of Vision Inspite of all precautions and proactive action,our eyes may develop some defects due to various reasons. Three of the common optical defects of eye are

Myopia or short sightedness or near sightedness, Hypermetropiaor long sightedness or farsightedness Presbyopia or old sightedness

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M yopia, also called, common name nearsightedness for impaired vision in which a person sees near objects clearly while distant objects appear blurred.

In normal vision, light rays from an object enter the eye and are focused by the lens (transparent tissue that changes shape to focus incoming light) onto the retina (the membrane at the back of the eye that transmits images of external objects to the optic nerve). In people with nearsightedness, the distance between the lens and the retina is too long. As a result, light rays from distant objects focus before they strike the retina. Near objects appear clearly because light rays from them focus correctly on the retina.Nearsightedness is corrected with a diverging lens.

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Possible causes are :i) Increase in the size of eye ball i.e. distance of the retina from eye lens increases.ii) Decrease in the focal length of the eye lens, when the eye is fully relaxed.

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H ypermetropia, also called, common name farsightedness for a defect in vision in which a person sees near objects with blurred vision, while distant objects appear in sharp focus.

In normal vision, light rays from an object entering the eye are focused by the lens (transparent tissue that changes shape to helpfocus incoming light) on the retina (the membrane at the back of the eye that transmits images of external objects to the optic nerve). In people with farsightedness, the distance between the lensand the retina is too short. As a result, light rays from near objects strike the retina before they are in focus, which causes blurred vision. Distant objects appear clearly because light rays from them focus correctly on the retina.Farsightedness is corrected with a converging lens.

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Possible causes are :i) Contraction in the size of eye ball i.e. distance of the retina from eye lens decreases.ii) Increase in the focal length of the eye lens, when the eye is fully relaxed.

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P resbyopia, also called old sightedness:With increasing age ,the cilliary muscles holding the eye the eye lens weaken and eye loses some of its elasticity. Therefore power accommodation of eye decreases with age.This defect is called Presbyopia. Bifocal lenses are used in such cases.

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TheCamera

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Basic Camera Function(Photographic camera)

In its simplest form, the camera is a light-tight container carrying a lens, a shutter, a diaphragm, a device for holding (and changing) the film in the correct image plane, and a viewfinder to allow the camera to be aimed at the desired scene.

The lens projects an inverted image of the scene in front of the camera onto the film in the image plane. The image is sharp only if the film

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is located at a specific distance behind the lens. This distance dependson the focal length of the lens and the distance of the object in front ofthe lens. To photograph near and far subjects, all but the simplest cameras have a focusing adjustment that alters the distance between the lens and the film plane to make objects at the selected distance produce a sharp image on the film. In some cameras focusing adjustment is achieved by moving only the front element or internal elements of the lens, in effect modifying the focal length.

The shutter consists of a set of metallic leaves mounted in or behind the lens or a system of blinds positioned in front of the film. It can be made to open for a predetermined time to expose the film to the image formed by the lens. The time of this exposure is one of the two factors controlling the amount of light reaching the film. The other factor is the lens diaphragm, or aperture, an opening with an adjustable diameter. The combination of the diaphragm opening and exposure time is the photographic exposure. To obtain a film image that faithfully records all the tone gradation of the object, this exposure must be matched to the brightness (luminance) of the subject and to the sensitivity or speed of the film. Light meters built into most modern cameras measure the subject luminance and set the shutter orthe lens diaphragm to yield a correctly exposed image.

• The MicroscopePhysics : Ray Optics

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Simple microscope or magnifying glassA

simple microscope is used for observing magnified images of tinyobjects. It consists of a converging lens of small focal length. A virtual erect and magnified image of the object is formed at the least distance of distinct vision from the eye held close to the lens.That is why simple microscope is also called a magnifying glass.

A Magnifying glass magnifying an object

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Compound microscopeAcompound microscope is an optical instrument used for observing highly magnified images of tiny objects.

Construction:Two convex lenses form a compound microscope. The object lens ispositioned close to the object to be viewed. It forms an upside-down and magnified image called a real image because the light rays actually pass through the place where the image lies. The ocular lens, or eyepiece lens, acts as a magnifying glass for this real image. The ocular lens makes the light rays spread more, so that they appear to come from a large inverted image beyond the object lens. Because light rays do not actually pass through this location, the image is called a virtual image.

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A compound microscope

TheTelescopeTelescope is an instrumentused to see distant objects which cannot be seen by naked eyes.Two types:

Refracting type telescope:Telescope in which the objective is convex lenswhich use phenomenon of refraction.Eg. Astronomical telescope, terrestrial telescope, galileo telescope, etc.

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Refraction type telescope

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Galileo Galilei born Feb. 15, 1564, Pisa [Italy] -died Jan. 8, 1642

Galileo's career took a dramatic turn. In the spring of 1609 he heard that in the Netherlands an instrument had been invented that showed distant things as though they were nearby. By trial and error, he quickly figured out the secret of the invention and made his own three-powered spyglass from lenses for sale in spectacle makers' shops. Others had done the same; what set Galileo apart was that hequickly figured out how to improve the instrument, taught himself the art of lens grinding, and produced increasingly powerful telescopes. In August of that year he presented an eight-powered instrument to the Venetian Senate (Padua was in the Venetian Republic). He was rewarded with life tenure and a doubling of his salary. Galileo was now one of the highest-paid professors at the university.In the fall of 1609 Galileo began observing the heavens with instruments that magnified up to 20 times. In December he drew the Moon's phases as seen through the telescope, showing that the Moon's surface is not smooth, as had been thought, but is rough and uneven. In January 1610 he discovered four moons revolving around Jupiter. He also found that the telescope showed many more stars than are visible with the naked eye. These discoveries were earthshaking, and Galileo quickly produced a little book, SidereusNuncius (The Sidereal Messenger), in which he described them. He dedicated the book to Cosimo II de Medici (1590–1621), the grand duke of his native Tuscany, whom he had tutored inmathematics for several summers, and he named the moons of Jupiter after the Medici family: the SideraMedicea, or “Medicean Stars.” Galileo was rewarded with an appointment as mathematician and philosopher of the grand duke of Tuscany, and in the fall of 1610 he returned in triumph to his native

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land.

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Reflecting typetelescope: Telescope in which the objective is concave mirror which use phenomenon of reflection. Eg. Newtonian telescope, cassegrain telescope, etc.

NewtonianReflectingtelescope

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Early Telescopes

Although a Dutch optician probably designed the first telescope, it was Galileo who turned it rigorously on the heavens in the early 17th century. Galileo used a refracting telescope (top) with a convex lens atthe front and a concave lens at the viewing end. The 18th-century

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refracting telescope (middle) produced images that were blurred because of the different indexes of its combined lenses. The bottom scope is a reflecting telescope, which used two mirrors and an eyepiece lens, a setup that eliminates the problems of long viewing tubes and color distortion.

Telescopes of the World

Large telescopes are found all over the world. Most large telescopes are based on high mountaintops, where Earth's atmosphere is thinner and

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does not interfere as much with light from distant star

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Hubble Space Telescope(HST): onboard Discovery space shuttle

The most sophisticated optical observatory ever placed into orbit around Earth. Earth's atmosphere obscures ground-based astronomers' view of celestial objects by absorbing or distorting light rays from them. A telescope stationed in outer space is entirely above the atmosphere, however, and receives images of much greater brightness, clarity, and detail than do ground-based telescopes with comparable optics.The HST is a large reflecting telescope whose mirror optics gather light from

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celestial objects and direct it into two cameras and two spectrographs. The HST hasa 2.4-metre (94-inch) primary mirror, a smaller secondary mirror, and various recording instruments that can detect visible, ultraviolet, and infrared light. The most important of these instruments, the wide-field planetary camera, can take either wide-field or high-resolution images of the planets and of galactic and extragalactic objects.

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Chandra X-Ray Observatory

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U.S. satellite, one of the National Aeronautics and Space Administration (NASA) fleet of “Great Observatories” satellites, which is designed to make high-resolution images of celestial X-ray sources. In operation since 1999 .

It is named in honour of Subrahmanyan Chandrasekhar, apioneer of the field of stellar evolution.

Breaking News6Oct, 2012

Melbourne : World’s powerful telescope made in Australia to fast the discovery of planets and rest of the huge galaxy that cost 400 million dollars($) and has a storing data capacity at the rate of 40GB per second.It is held inMerksenin west Australia inaugurated on Friday.

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Multiple Mirror Telescope

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The Multiple Mirror Telescope (MMT) located on Mount Hopkins near Tucson, Ariz., combines the light collected by its six computer-controlled mirrors into a single image.

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Green Bank Telescope

The National Radio Astronomy Observatory's Green Bank Telescope, Green Bank, W.Va

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