For those fortunate souls who do not need glasses, the lens ofthe eye adjusts its focal length in order to form a proper image onthe retina. This typically means that very distant objects as wellas objects as close as 25 cm can be seen clearly. Many of us needcorrective lenses since the lens in our eye cannot adjustsufficiently to produce a clear image over the full range objectdistances. This may be because the lens itself does not adjust wellor because the eye is either longer or shorter than ‘normal’. Inthe case of someone who is nearsighted (can see up close) the eyemay only be able to see clearly items up to 50cm or 1m away (thiswould be the far point). In order to see something further away, alens (either glasses or contacts) is used to produce a virtualimage of a distant object at the person’s far point. Their eye canthen accommodate the rest of the way and produce a clear image.Suppose a person who has a far point of 63.0 cm is trying to view adistant object. What is the focal length (with correct sign) of alens that would take a distant object and make an image on the sameside of the lens as the object a distance 63.0 cm from the lens?Incorrect.
Is the lens converging or diverging?
Lenses are prescribed in terms of their refractive power, whichis expressed in terms of diopters (see the text or your favoritesearch engine for the definition of a diopter). What is therefractive power of this lens in terms of diopters? (do not enterunits.)
In the case of someone who is farsighted, the eye is not able tofocus clearly on objects closer than a certain distance. Thisclosest point on which a person’s eye can focus is called the nearpoint. In this situation the corrective lens is used to make anobject closer than the near point produce an image further awayfrom the lens at the near point. Suppose a person who has a nearpoint of 53.1 cm is trying to view a book at a distance of 25.0 cm.What is the focal length (with correct sign) of a lens that wouldtake the book and make an image on the same side of the lens as thebook a distance 53.1 cm from the lens?
Is the lens converging or diverging?
What is the refractive power of this lens in terms of diopters?(do not enter units.)
