A Manual of Ophthalmic Practice |
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Page 5
... focus of a lens is the point where the refracted rays or their pro- longations meet . Double convex lenses have what are known as real and virtual foci . Real foci . - We will first consider the case in which the luminous rays falling ...
... focus of a lens is the point where the refracted rays or their pro- longations meet . Double convex lenses have what are known as real and virtual foci . Real foci . - We will first consider the case in which the luminous rays falling ...
Page 6
... focus , but so near that all incident rays of light form a divergent pencil , as shown ( Fig . 6 ) . The L F BAD FIG . 6 . luminous point being at L , by comparing the path of the diverging ray LB with that of the ray SB parallel to the ...
... focus , but so near that all incident rays of light form a divergent pencil , as shown ( Fig . 6 ) . The L F BAD FIG . 6 . luminous point being at L , by comparing the path of the diverging ray LB with that of the ray SB parallel to the ...
Page 7
... focus F. As all rays from the point L cut the axis approximately at 7 , this point is what is called the conjugate focus of the point L. The term con- jugate focus expresses the relation existing between the two points L and 7 , which ...
... focus F. As all rays from the point L cut the axis approximately at 7 , this point is what is called the conjugate focus of the point L. The term con- jugate focus expresses the relation existing between the two points L and 7 , which ...
Page 8
... focus , but the prolongations of these rays in the opposite direction cut one another in a point F , which is the principal virtual focus . In the case in which the rays proceed from some point L on the axis , and form a diverging ...
... focus , but the prolongations of these rays in the opposite direction cut one another in a point F , which is the principal virtual focus . In the case in which the rays proceed from some point L on the axis , and form a diverging ...
Page 9
... focus is formed at 7 , which is between the principal focus and K G C L FIG . 9 . the lens and which may be considered the conjugate focus of the point L. Optical centre and secondary axis . - In every lens there is a point called the ...
... focus is formed at 7 , which is between the principal focus and K G C L FIG . 9 . the lens and which may be considered the conjugate focus of the point L. Optical centre and secondary axis . - In every lens there is a point called the ...
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Common terms and phrases
accommodation affected amblyopia anomaly of refraction anterior chamber appear asthenopia astigmatism atrophy atropine axis bandage become blood cataract cause centre chamber choroid ciliary region colour commenced concave lens congenital conjunctiva convergence convex lens cornea corneal margin corneitis curette curvature degree of myopia dilated dioptric direction disease displacement distance emmetropic examination extraction eyeball eyelids forceps foreign body fundus glasses glaucoma globe hæmorrhage horizontal hypermetropia hypermetropic astigmatism incision increased inflammation inflammatory injury intolerance of light iridectomy iris iritis keratitis knife lachrymal lenses less lids lines lint lotion muscle myopia object occur ocular opacity opaque operation ophthalmia ophthalmoscope optic disc orbit pain paralysis passed patient performed portion posterior presbyopia pupil rays of light removed retina retinal vessels right angles scissors sclerotic seen sight spots staphyloma strabismus suppuration surface sutures sympathetic ophthalmia symptoms synechia syphilitic tension tion treatment tumour ulceration usually vitreous wire speculum wound
Popular passages
Page 318 - Walsham, besides being an excellent surgeon, is a teacher in its best sense, and having had very great experience in the preparation of candidates for examination, and their subsequent professional career, may be relied upon to have carried out his work successfully. Without following out in detail his arrangement, which is excellent, we can at once say that his book is an embodiment of modern ideas neatly strung together, with an amount of careful organisation well suited to the candidate, and,...