7-1 PRENTICE HALL ©2008 Pearson Education, Inc. Upper Saddle River, NJ FORENSIC SCIENCE An Introduction By Richard Saferstein THE MICROSCOPE Chapter 7

7-2 PRENTICE HALL ©2008 Pearson Education, Inc. Upper Saddle River, NJ FORENSIC SCIENCE An Introduction By Richard Saferstein Introduction A __________ is an optical instrument that uses a lens or a combination of lenses to magnify and resolve the fine details of an object. The earliest methods for examining physical evidence relied solely on the microscope. The magnified image seen by looking through a lens is known as a __________ image, whereas an image viewed directly is known as a _________ image. The object to be magnified is placed under the lower lens, called the objective and viewed through the upper lens, called the eyepiece. Various types of microscopes are used to analyze forensic specimens.

7-3 PRENTICE HALL ©2008 Pearson Education, Inc. Upper Saddle River, NJ FORENSIC SCIENCE An Introduction By Richard Saferstein The Compound Microscope In the basic _________ microscope, the object to be magnified is placed under the lower lens (_________ lens) and the magnified image is viewed through the upper lens (_________ lens). The magnification of the image can be calculated by __________ the magnifying power of the objective lens times the magnifying power of the eyepiece lens. The microscope is composed of a mechanical system which supports the microscope, and an optical system which illuminates the object under investigation and passes _________ through a series of lens to form an image of the specimen.

7-4 PRENTICE HALL ©2008 Pearson Education, Inc. Upper Saddle River, NJ FORENSIC SCIENCE An Introduction By Richard Saferstein The Compound Microscope The Mechanical System –__________: the support. –__________: the C-shaped upright structure. –__________: the plate on which the specimens are placed. –__________: the hollow tube on which the objectives and eyepiece lenses are mounted. –__________ Adjustment: the knob used to focus the microscope lenses by moving the body tube. –_________ Adjustment: the knob also used to focus the lenses by moving the body tube, but by a much smaller magnitude.

7-5 PRENTICE HALL ©2008 Pearson Education, Inc. Upper Saddle River, NJ FORENSIC SCIENCE An Introduction By Richard Saferstein The Compound Microscope The Optical System –Illuminator: artificial light, usually supplied by a lightbulb, to illuminate the specimen. Transmitted Illumination: when the light is directed up through the specimen from the base. Vertical or Reflected Illumination: when the light comes from above and reflects off the specimen. –Condenser: lens system under the microscope stage that focuses light onto the specimen.

7-6 PRENTICE HALL ©2008 Pearson Education, Inc. Upper Saddle River, NJ FORENSIC SCIENCE An Introduction By Richard Saferstein The Compound Microscope The Optical System –Objective Lens: the lens _________ to the specimen; usually several objectives are mounted on a revolving __________. Parafocal: when the microscope is focused with one objective in place, another objective can be rotated into place and the specimen remains very nearly in correct focus. –Eyepiece or Ocular Lens: the lens closest to the _________. Monocular: a microscope having only _________ eyepiece. Binocular: a microscope having _________ eyepieces.

7-7 PRENTICE HALL ©2008 Pearson Education, Inc. Upper Saddle River, NJ FORENSIC SCIENCE An Introduction By Richard Saferstein The Comparison Microscope The comparison microscope consists of two independent _________ lenses joined together by an optical bridge to a common eyepiece lens. When a viewer looks through the eyepiece lens of the comparison microscope, the objects under investigation are observed side-by-side in a circular field that is equally divided into ________ parts. Modern __________ examination began with the introduction of the comparison microscope, with its ability to give the firearms examiner a side-by-side magnified view of bullets.

7-8 PRENTICE HALL ©2008 Pearson Education, Inc. Upper Saddle River, NJ FORENSIC SCIENCE An Introduction By Richard Saferstein The Stereoscopic Microscope The stereoscopic microscope is actually two __________ compound microscopes properly spaced and aligned to present a three- dimensional image of a specimen to the viewer, who looks through both eyepiece lenses. It is particularly useful for evidence not requiring very ________ magnification (10x- 125x). Its large working distance makes it quite applicable for the microscopic examination of _________, bulky items.

7-9 PRENTICE HALL ©2008 Pearson Education, Inc. Upper Saddle River, NJ FORENSIC SCIENCE An Introduction By Richard Saferstein Polarizing Microscopy Light that is confined to a single plane of _________ is said to be plane- polarized. The examination of the interaction of plane-polarized light with matter is made possible with the polarizing microscope. Polarizing microscopy has found wide applications for the study of __________ materials (materials that split a beam of light in two, each with its own refractive index value). The determination of these refractive index data provides information that helps to identify minerals present in a soil sample or the identity of a man-made fiber.

7-10 PRENTICE HALL ©2008 Pearson Education, Inc. Upper Saddle River, NJ FORENSIC SCIENCE An Introduction By Richard Saferstein The Microspectrophotometer The microspectrophotometer is a spectrophotometer coupled with a _________ microscope. The examiner studying a specimen under a microscope can simultaneously obtain the __________ absorption spectrum or IR spectrum of the material being observed. This instrument is especially useful in the examination of trace evidence, ________, fiber, and ink evidence.

7-11 PRENTICE HALL ©2008 Pearson Education, Inc. Upper Saddle River, NJ FORENSIC SCIENCE An Introduction By Richard Saferstein The Scanning Electron Microscope Finally, the scanning electron microscope (SEM) bombards a specimen with a beam of _________ instead of light to produce a highly magnified image from 100x to 100,0000x. Its depth of focus is some _________ times better than optical systems at similar magnification. The bombardment of the specimen’s surface with electrons normally produces _________ emissions that can be used to characterize elements present in the material under investigation.