Eye-lens sentence example

  • When the axis of the eye-lens coincides with that of the object-glass, and the focal point of the eye-lens is coincident with the principal focus of the object-lens, parallel rays.
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  • The magnifying power obviously depends on the proportion of the focal length of the object-lens to that of the eye-lens, that is, magnifying power where F is the focal length of the object-lens and e that of the eye-lens.
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  • Also the diameter of the pencil or parallel rays emerging from the eye-lens to the diameter of the object-lens inversely as, the magnifying power of the telescope.
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  • The substitution of a positive or negative eye-piece for the simple convex or concave eye-lens, and of an achromatic object-glass for the simple object-lens, transforms these, early forms into the modern achromatic telescope.
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  • The mere size of the apparent field of view depends upon obtaining the oblique pencils of light emerging from it to cross the axis at the great possible angle, and to this end the presence of a field-lens is indispensable, which is separated from the eye-lens by a considerable interval.
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  • There are also other eye-pieces having the field-lens double or achromatic as well as the eye-lens.
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  • In cases where it is important to get the maximum quantity of light into the eye, the field-lens is discarded and an achromatic eye-lens alone employed.
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  • The eye-lens converts diverging pencils into parallels.
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  • In this type the eye-lens is about twice as powerful as the collective lens, and makes the rays parallel.
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  • The weak compensation oculars resemble a Huygenian eyepiece with achromatic eye-lens, whilst the more powerful ones are of a different construction.
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  • The eye-lens can be adjusted for the thread-plate, so that different observers can see the cross clearly.
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  • To determine the position of the anterior focal plane of the eyepiece, the eyepiece is placed on the stage with the eye-lens downwards.
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