(a) Suppose the \"relaxed\" focal length f of theeffective thin lens of the eye
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Question
(a) Suppose the "relaxed" focal length f of theeffective thin lens of the eye is 2.58 cm.This means that the far-objects will be focussed at its focalpoint, behind the lens, in this case at the retina of the eye. Ifan object is located at a distance p = 48.8 cm, what focal length f ' of theeffective thin lens is required for the object to be seenclearly?
1 cm
(b) Do the Ciliary muscles increase or decrease the radii ofcurvature of the eye lens to produce focal length f'?
HRW7 34-91P Figure35-34a shows the basic structure of a human eye. Lightrefracts into the eye through the cornea and is then furtherredirected by a lens whose shape (and thus ability to focus thelight) is controlled by muscles. We can treat the cornea and eyelens as a single effective thin lens (Fig. 35-34b). If themuscles are relaxed, a ^''normal^'' eye focuses parallel light raysfrom a distant object O to a point on the retina at theback of the eye, where processing of the visual information begins.As an object is brought close to the eye, the muscles change theshape of the lens so that rays form an inverted real image on theretina (Fig. 35-44c). (a) Suppose the ^''relaxed^'' focal length f of theeffective thin lens of the eye is 2.58 cm.This means that the far-objects will be focussed at its focalpoint, behind the lens, in this case at the retina of the eye. Ifan object is located at a distance p = 48.8 cm, what focal length f ^' of theeffective thin lens is required for the object to be seenclearly? cm (b) Do the Ciliary muscles increase or decrease the radii ofcurvature of the eye lens to produce focal length f^'? theydon^'t change the radii decrease notenough information given increaseExplanation / Answer
(a)the object distance corresponding to this image distancecan be calculated from the thin lens equation: (1/p) + (1/D) = (1/f') p = 48.8 cm and D = -25 cm (b)Light entering the eye passes through a transparentstructure called the cornea,behind which are a clear liquid (theaqueous humor),a variable aperture (the pupil,which is an openingin the iris),and the crystalline lens.Most of the refration occursat the outer surface of the eye,where the cornea is covered with afilm of tears.The iris regulates the amount of light entering theeye by dilating,or opening,the pupil in low-light conditions andcontracting,or closing,the pupil in high-light conditions.Thef-number range of the human eye is approximately (f/2.8) to(f/16).Therefore,the Ciliary muscles don't change the radii.Related Questions
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