Scientific Dialogues: Intended for the Instruction and Entertainment of Young People, Inwich the First Principles of Natural and Experimental Philosophy are Fully Explained. Vol. II, IV-VI.J. Johnson, 1809 |
From inside the book
Results 1-5 of 14
Page 53
... area of the glass is to the area of the focus of course , it may be a hundred or even a thousand timest greater in the one case than in the other .. James . Have I not heard you say that Mr. F 3 OF THE FOCAL DISTANCE . 53.
... area of the glass is to the area of the focus of course , it may be a hundred or even a thousand timest greater in the one case than in the other .. James . Have I not heard you say that Mr. F 3 OF THE FOCAL DISTANCE . 53.
Page 67
... distance from the glass is greater or less than the distance of the object ; if A B C ( Fig . 12. ) be the object , eb A will be the picture ; and if cb A be the object , A B C will be the pic- ture . Charles . Is ... FOCAL DISTANCE . 67.
... distance from the glass is greater or less than the distance of the object ; if A B C ( Fig . 12. ) be the object , eb A will be the picture ; and if cb A be the object , A B C will be the pic- ture . Charles . Is ... FOCAL DISTANCE . 67.
Page 186
... focal distance of the object- glass is greater than the focal di- stance of the eye - glass . Thus , if the focal distance of the object - glass is ten inches , and that of the eye - glass only a single inch , the telescope magnifies ...
... focal distance of the object- glass is greater than the focal di- stance of the eye - glass . Thus , if the focal distance of the object - glass is ten inches , and that of the eye - glass only a single inch , the telescope magnifies ...
Page 187
... distance only of a single yard . James . Is there no advantage gained , if the focal distance of the eye - glass , and of the object - glass , be equal ? Tutor . None ; and therefore in telescopes of this kind we have only to increase the ...
... distance only of a single yard . James . Is there no advantage gained , if the focal distance of the eye - glass , and of the object - glass , be equal ? Tutor . None ; and therefore in telescopes of this kind we have only to increase the ...
Page 188
... focal distance , will require an eye - glass whose focal distance is rather more than two inches and a half : and an object- glass with a focal distance of a hun- dred feet , must have an eye - glass whose focus must be about six inches ...
... focal distance , will require an eye - glass whose focal distance is rather more than two inches and a half : and an object- glass with a focal distance of a hun- dred feet , must have an eye - glass whose focus must be about six inches ...
Common terms and phrases
A B C A B Plate angle of incidence angle of reflection appear attract body called Charles colours compass concave lens concave mirror CONVERSATION convex lens convex mirror dark diameter direction distinct vision diverge double convex equal eye-glass farther feet figure flected focal distance focus of parallel formed half humours inches incident rays inverted image iron James ject lenses Let A B light flowing look looking-glass magnifying power means microscope move nearer needle nosegay object object-glass optic optic nerve painted parallel rays pass pencil of rays perpendicular piece plain mirror Plate 11 proceed radius rainbow rays fall rays flowing rays of light reflected rays reflecting telescope refraction retina seen shutter side small hole south pole spectator stance stand steel Suppose surface throw tion transparent tube Tutor violet vitreous humour
Popular passages
Page 80 - Seasons return, but not to me returns Day, or the sweet approach of ev'n or morn, Or sight of vernal bloom, or summer's rose, Or flocks or herds or human face divine ; But cloud instead, and ever-during dark Surrounds me, from the cheerful ways of men Cut off, and for the book of knowledge fair Presented with an universal blank Of nature's works, to me expung'd and ras'd, And wisdom at one entrance quite shut out.
Page 85 - First the flaming red Sprung vivid forth ; the tawny orange next ; And next delicious yellow ; by whose side Fell the kind beams of all-refreshing green. Then the pure blue, that swells autumnal skies, Ethereal...
Page 8 - How distant some of these nocturnal suns ! So distant (says the sage) 'twere not absurd To doubt, if beams, set out at nature's birth, Are yet arriv'd at this so foreign world ; Though nothing half so rapid as their flight.
Page 109 - ... as the angle of reflection is always equal to the angle of incidence, the image for any point can be seen only in the reflected ray prolonged.
Page 166 - Meantime, refracted from yon eastern cloud, Bestriding earth, the grand ethereal bow Shoots up immense; and every hue unfolds, In fair proportion, running from the red To where the violet fades into the sky.
Page 172 - Died in the fainting Violet away. These, when the clouds distil the rosy shower, Shine out distinct adown the watery bow ; While o'er our heads the dewy vision bends Delightful, melting on the fields beneath. Myriads of mingling dyes from these result, And myriads still remain ; infinite source Of beauty, ever blushing, ever new. Did ever poet image aught so fair, Dreaming in whispering groves, by the hoarse brook; Or prophet, to whose rapture heaven descends...
Page 187 - Yes; the three glasses next the eye baving their focal distances equal, the magnifying power is found by dividing the focal distance of the object-glass by the focal distance of one of. the eye-glasses.
Page 49 - A lens is glass ground into such a form, as to collect or disperse the rays of light which pass through it. These are of different shapes, and from thence receive different names.
Page 61 - If anoto glass, FG, of the same convexity as DE, be placed in the rays at the same distance from the focus, it will refract them so, as that, after going out of it, they will be all parallel...