Conversations on Natural Philosophy: In which the Elements of that Science are Familiarly Explained and Adapted to the Comprehension of Young Pupils : Illustrated with PlatesJ.Y. Humphreys, 1821 - 311 من الصفحات |
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الصفحة 231
... which proceed straight forwards . The whole of the vibrations are thus collected into a focus ; and if the ear be situated in or near that spot , the sound is prodigiously increased . Figure 7. plate XIV . will ON WIND AND SOUND . 231.
... which proceed straight forwards . The whole of the vibrations are thus collected into a focus ; and if the ear be situated in or near that spot , the sound is prodigiously increased . Figure 7. plate XIV . will ON WIND AND SOUND . 231.
الصفحة 232
... focus at F. The trumpet used by deaf persons acts on the same principle ; but as the voice enters the trumpet at the large instead of the small end of the instrument , it is not so much confined , nor the sound so much increased . Emily ...
... focus at F. The trumpet used by deaf persons acts on the same principle ; but as the voice enters the trumpet at the large instead of the small end of the instrument , it is not so much confined , nor the sound so much increased . Emily ...
الصفحة 266
... focus of the mirror . Caroline . Pray , what is the meaning of focus ? Mrs. B. A point at which converging rays unite . And it is in this case called an imaginary focus ; because the rays do not really unite at that point , but only ...
... focus of the mirror . Caroline . Pray , what is the meaning of focus ? Mrs. B. A point at which converging rays unite . And it is in this case called an imaginary focus ; because the rays do not really unite at that point , but only ...
الصفحة 267
... focus in the direction of the axis of the mirror , at a point equally distant from the centre and the surface of the sphere , and this point is not an imaginary focus , as happens with the convex mirror , but is the true focus at which ...
... focus in the direction of the axis of the mirror , at a point equally distant from the centre and the surface of the sphere , and this point is not an imaginary focus , as happens with the convex mirror , but is the true focus at which ...
الصفحة 268
... focus , L , than parallel rays ; their focus is therefore nearer to the mirror M N. Divergent rays are brought to a more distant focus than parallel rays , as in fig . 5 , where the focus is at L ; but the true focus of mirrors , either ...
... focus , L , than parallel rays ; their focus is therefore nearer to the mirror M N. Divergent rays are brought to a more distant focus than parallel rays , as in fig . 5 , where the focus is at L ; but the true focus of mirrors , either ...
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عبارات ومصطلحات مألوفة
angle appear atmosphere attraction axis ball called camera obscura Caroline centre of gravity centrifugal force circle cohesion colored rays concave mirror consequently convex cricket ball dark degrees descend dimensions diminishes direction distance diurnal motion draw earth eclipse effect elastic Emily equal equator equilibrium fixed stars fluids focus fulcrum glass globe greater heat heavier inclined plane lens less lever lighter luminous body mechanical power mercury meridian moon move nature object observe opaque body opposite orbit particles passes perfectly perpendicularly planets plate pole Pray pressure proceed produced proportion pulley pump quantity rays fall rays of light re-action recollect reflected rays refraction represents reservoir resistance retina revolution revolve round rise round the sun screw shadow shine situated solid bodies sonorous body space specific gravity sphere string sun's rays supported suppose surface tides tion tube understand velocity vibrations weight wheel whilst wind
مقاطع مشهورة
الصفحة 126 - ... things clad; Silence accompanied; for beast and bird, They to their grassy couch, these to their nests Were slunk, all but .the wakeful nightingale; She all night long her amorous descant sung; Silence was pleased: now...
الصفحة 140 - evidence of things not seen," in the fulness of Divine grace ; and was profound on this, the greatest concern of human life, while unable even to comprehend how the " inclination of the earth's axis to the plane of its orbit" could be the cause of the change of the seasons.
الصفحة 125 - Now came still evening on, and twilight gray Had in her sober livery all things clad ; Silence accompanied ; for beast and bird, They to their grassy couch, these to their nests Were slunk, all but the wakeful nightingale ; She all night long her amorous descant sung...
الصفحة 98 - ... time that the axle describes a small one, therefore the power is increased in the same proportion as the circumference of the wheel is greater than that of the axle. If the...
الصفحة 291 - The construction of the eye is so admirable, that it is capable of adapting itself, more or less, to the circumstances in which it is placed. In a faint light the pupil dilates so as to receive an additional quantity of rays, and in a strong light it contracts, in order to prevent the intensity of the light from injuring the optic nerve.
الصفحة 103 - When, therefore, the surfaces of the two bodies come into contact, the prominent parts of the one will often fall into the hollow parts of the other, and occasion more or less resistance to motion. In proportion as the surfaces of bodies are well polished, the friction is diminished; but it is always considerable, and it is usually computed to destroy one-third of the power of a machine.
الصفحة 43 - ... regions. The pressure of the atmosphere has been compared to that of a pile of fleeces of wool, in which the lower fleeces are pressed together by the weight of those above : these lie light and loose, in proportion as they approach the uppermost fleece, which receives no external pressure, and is confined merely by the force of its own gravity.
الصفحة 76 - The curve-line which the ball has described, is called in geometry, a parabola; but when the ball is thrown perpendicularly upwards, it will descend perpendicularly ; because the force of projection, and that of gravity, are in the same line of direction. We have noticed the centres of magnitude, and of motion ; but I have not yet explained to you what is meant by the centre of gravity ; it is that point in a body, about which all the parts exactly balance each other ; if, therefore, that point is...
الصفحة 294 - By the assistance of such glasses, therefore, the rays from a distant object fall on the pupil as divergent as those from a less distant object ; and, with short-sighted people, they throw the image of a distant object back as far as the retina.
الصفحة 301 - XY (fig. 2.) in it, to converge the rays to a focus on the object A B. There is but one thing more wanting to complete .the solar microscope, which I shall leave to Caroline's sagacity to discover. CAROLINE. Our microscope has a small mirror attached to it, upon a moveable joint, which can be so adjusted as to receive the sun's rays, and reflect them upon the object. If a similar mirror were placed to reflect light upon the lens, would it not be a means of illuminating the object more perfectly?...