High-Q | 8 סימולציה

45

סימולציה מס' 8

פרק שני

– אנגלית

Text II (Questions 18-22)

The instrument normally brought to mind by the word "microscope" is a compound microscope of the type commonly used by biologists, doctors, and medical researchers. In its simplest form, as made in the 17th century, it consisted of two optical elements - the 'objective lens', located close to the object under study, and at some distance from the objective (usually about 150 millimeters) a second lens, which served as the eyepiece. 5 Many of today's microscopes are of the same basic construction except that the objective and eyepiece components are not single simple lenses, but are each made of two or more optical elements. In its basic form, the body of the microscope is a simple tube mounted on a stand. The tube has the objective at the lower end and the eyepiece at the upper end. The upper portion 10 of the body is usually equipped with means of accepting different types of 'heads', for holding the eyepieces. Three types of heads are in common usage - monocular, binocular, and triocular. Their names refer to the number of eyepieces that can be accommodated. The binocular head is much to be preferred over the monocular if a great deal of time is to be spent making observations. The third outlet of the triocular head provides for a camera, 15 making it possible to photograph the specimen while observing it. Microscopes also have a third optical component, a mirror which is mounted on the base of the microscope stand. The mirror reflects the light from an illumination source onto the specimen. The specimen, mounted on a transparent glass slide and usually covered with a thin cover glass, is placed between the mirror and the objective. 20

Questions

18. According to the passage, the simplest microscopes, as made in the 17th century, had -

(1) one lens (2) two lenses (3) three lenses (4) four or more lenses

19. It can be inferred from the second paragraph that -

(1) monocular heads are more commonly used than the binocular head (2) it is impossible to photograph a specimen while observing it (3) binocular heads are more comfortable than monocular heads (4) the triocular head enables two people to observe a specimen simultaneously

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