Optical Instrument12345678123456712.pptx

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1. Raymond A. Serway Chris Vuille 1 Optical Instruments

2. Analysis generally involves the laws of reflection and refraction. Analysis uses the procedures of geometric optics (Ray model of light). However, To explain certain phenomena, the wave nature of light must be used. Introduction 2

3. The cornea- lens system focuses light onto the back surface of the eye. This back surface is called the retina. The retina contains receptors called rods and cones. These structures send impulses via the optic nerve to the brain. The brain converts these impulses into our conscious view of the world. 3 Section 25.2

4. Cornea – - a round, transparent dome that acts as the outer window of the eye - it focuses that light that enters the eye Aqueous Humor – clear liquid behind the cornea Lens – it is transparent, elastic and crystalline - its role is to focus the light and move towards the retina 4 Section 25.2 Parts of the Human Eye and their Function s

5. Uvea - it forms the center of the eyeball 3 Parts Choroid – a thin membrane that is placed between outer protective sclera and retina…. To prevent the rays of light bouncing off on the back side of the eye. Ciliary Body – to assist in the adjustment of the shape of the lens. Iris – described as a separate part in this section of article 5 Section 25.2 Parts of the Human Eye and their Function s

6. The iris is the colored portion of the eye. It 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. 6 Section 25.2

7. Pupil - the hole in the middle of the eye which allow light to pass through Optic Nerve – the prolongation of the axons of the ganglion cells in the retina - It connects eye to the brain Sclera – the whitish, opaque part of the eye which is linked to the cornea. Retina – The sensory membrane of the eye. 7 Section 25.2 Parts of the Human Eye and their Function s

8. Vitreous Humor – the jelly like substance that exist within the interior chamber after the lens -parts of the eye that delivers pressure inside the eye and keep it inflated Fovea –a shallow pit in the middle of the retina that is free of the blood vessels and has the maximum concentration of cells sensitive to the color and brightness. Blood vessels – an artey , vein or capillary through which blood flows 8 Section 25.2 Parts of the Human Eye and their Function s

9. The blind spot – a small light sensitive area of the retina marking the point where nerve fibers from the retina cells converge to form the optic nerve. Hyaloid membrane – a transparent insubstantial membrane surrounding the transparent jelly or vitreous humor of the eye and separating it from the retina The muscle – a tissue that can undergo repeated contraction and relaxation, so that it is able to produce movement of the body parts, maintain tensions and pump fluids within the body 9 Section 25.2 Parts of the Human Eye and their Function s

10. Suspensory Ligament – provides support for an organ or other body parts especially a fibrous membrane that holds the lens of the eye 10 Section 25.2 Parts of the Human Eye and their Function s

11. Rods and Cones Chemically adjust their sensitivity according to the prevailing light conditions The adjustment takes about 15 minutes. This phenomena is “getting used to the dark ” Accommodation The eye focuses on an object by varying the shape of the crystalline lens through this process. An important component is the ciliary muscle which is situated in a circle around the rim of the lens. Thin filaments, called zonules , run from this muscle to the edge of the lens. 11 Section 25.2

12. Also called hyperopia The image focuses behind the retina. Can usually see far away objects clearly, but not nearby objects Section 25.2 20

13. A converging lens placed in front of the eye can correct the condition. The lens refracts the incoming rays more toward the principle axis before entering the eye. This allows the rays to converge and focus on the retina. 13 Section 25.2

14. Also called myopia In a myopia the nearsightedness is caused by the lens being too far from the retina. xial In refractive myopia , the lens- cornea system is too powerful for the normal length of the eye. 14 Section 25.2

15. A diverging lens can be used to correct the condition. The lens refracts the rays away from the principle axis before they enter the eye. This allows the rays to focus on the retina. 23 Section 25.2

16. The single- lens photographic camera is an optical instrument. Components Opaque, light- tight box Converging lens Produces a real image Film behind the lens Receives the image 37 Section 25.1

17. Image is formed on an electric device CCD – Charge-coupled device CMOS – Complementary metal- oxide semiconductor Both convert the image into digital form. The image can be stored in the camera’s memory. 38 Section 25.1

18. Proper focusing leads to sharp images. The lens-to- film distance will depend on the object distance and on the focal length of the lens. The shutter is a mechanical device that is opened for selected time intervals. Most cameras have an aperture of adjustable diameter to further control the intensity of the light reaching the film. With a small- diameter aperture, only light from the central portion reaches the film, and spherical aberration is minimized. 39 Section 25.1

19. Light intensity is a measure of the rate at which energy is received by the film per unit area of the image. The intensity of the light reaching the film is proportional to the area of the lens. The brightness of the image formed on the film depends on the light intensity. Depends on both the focal length and the diameter of the lens 40 Section 25.1