1) A 6.47 mm high firefly sits on the axis of, and 11.5 cm infront of, the thin lens A, whose focal length is 6.11 cm . Behindlens A there is another thin lens, lens B, with a focal length of20.7 cm . The two lenses share a common axis and are 61.5 cm apart.Is the image of the firefly that lens B forms real or virtual? Whatis the height of this image? Express the answer as a positivenumber (nm)?
image distance from lens B cm:
2)
One of the inevitable consequences of aging is a decrease in theflexibility of the lens. This leads to the farsighted conditioncalled presbyopia (elder eye). Almost every aging human willexperience it to some extent. However, for the myopic, ornearsighted, person it is possible that far vision will be limitedby a subpar far point and near vision will be hampered by anexpanding near point. One solution is to wear bifocal lenses thatare diverging in the upper half to correct the nearsightedness andconverging in the lower half to correct the farsightedness.
Suppose one such individual asks for your help. The patientcomplains that she can’t see far enough to safely drive (her farpoint dfar=114 cmd and she can’t read the font of her smart phonewithout holding it beyond arm’s length (her near point dnear=81.0cm? Prescribe the bifocals that will correct the visual issues foryour patient.
a)What is the focal length fns of the part of the bifocal lensthat corrects the patient's nearsightedness?
b) What is the focal length ffsffs of the part of the bifocallens that corrects the patient's farsightedness?
