CHAPTER 9 PHYSICS FOR JUNIOR HIGH SCHOOL VIII

OPTICAL TOOLS Optical tools : tools used to see by human  Natural : eye  Made : tools to help human in observing objects that can not be seen by naked-eye : camera, projector, magnifying glass, microscope, and telescope. PHYSICS FOR JUNIOR HIGH SCHOOL VIII

 Eye has its own parts, cornea, iris, pupil, lens, retina, and optical nerve. EYE PHYSICS FOR JUNIOR HIGH SCHOOL VIII

EYE  When our eye is relax (not accommodating), the lens becomes flat so that the focus space is the biggest, and the long space object is focused to retina.  Making the lens thick and flat(eye accommodation) in order to have the different space object can be focused by  The image in retina is real, inverse, and reduced. PHYSICS FOR JUNIOR HIGH SCHOOL VIII

THE RANGE OF SIGHT PP PR The range of sight Eye can see clearly if the object is in the range of sight, between near point (punctum proximum) and far point (punctum remontum). Normal eye  Near point = 25 cm  Far point = limitable = 25 cm = ∞= ∞ PHYSICS FOR JUNIOR HIGH SCHOOL VIII

 Defect is possible to occur if both far point and near point move from their proper position at normal eye (emetrop eye).  There are 3 kinds of eye defect caused by the moving of the far and near point, they are far sighted (myope), long-sighted (hypermyope), and old eye (presbyope). DEFECT OF EYE Gambar 9.3 Pembentukan bayangan pada mata: (a) Normal, (b) Miopi, (c) Hipermetropi Sumber : BSE VIII SMP PHYSICS FOR JUNIOR HIGH SCHOOL VIII

 Camera works almost like eye, it consists of one closed box that has a small whole in its front window. By the small whole the shaft of light then come in through the positive lens called objective. Objective lens forms the real image, inverse, and reduced at a film plate.  Camera has 3 light meter, namely range finder, shutter, and diaphragm. CAMERA PHYSICS FOR JUNIOR HIGH SCHOOL VIII

Function of the parts in camera a.Lens, to form the real image, reduced, and reverse. b.Film, as the place for image. c.Aperture (diaphragm gap), as the way of light to come in. diaphragm, to control the light coming through aperture. CAMERA PHYSICS FOR JUNIOR HIGH SCHOOL VIII

 Magnifying glass is the simplest optical tool, because it only consisting of one convex lens  Magnifying glass function is to observe small objects so that look bigger.  The type of image are virtual, standing, and zoomed.  There are 2 ways in using it, with accomodated eye, and non-accommodated eye. MAGNIFYING GLASS PHYSICS FOR JUNIOR HIGH SCHOOL VIII

 Microscope is a tool to observe super-small objects..  It has 2 convex lens, objective lens, and ocular lens.  Objective lens is a lens that is close to the observed-object.  Ocular lens is a lens that is close to observer’s eye. MICROSCOPE PHYSICS FOR JUNIOR HIGH SCHOOL VIII

 Telescope is an optical tool that is used for observing far objects so that look nearer.  It is discovered for the first time by Galileo Galilei.  There are 2 kinds of telescope, astronomical telescope, and earth telescope. TELESCOPE PHYSICS FOR JUNIOR HIGH SCHOOL VIII

 Periscope is a telescope that is used in submarine.  Periscope works to see the sea surface without come up the submarine.  Periscope consists of 2 convex lens, objective and ocular lens. And 2 isosceles angle-prism. PERISCOPE PHYSICS FOR JUNIOR HIGH SCHOOL VIII

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