Without her glasses, Dr.D.’s myopic eyes can only image objects that are, at most, 18.5cm awayfrom her eye(this is called her “far point”). Her “near point” (the closest she can image an object) is 10.5 cm from her eye. With this range of vision, she obviously needs glasses. Let’s say we want her glasses to allow her to see an object 20 feet away(not really the same as “20/20” vision.... but close enough).
You also need to note her glasses lenses are 1.5 cm in front of her eyes.
a) Make a sketch that you will use to determine all the distances in your imaging equation. Note the locations of: her eyes, her glasses, her near and far points, and the “far away object”.
b) Determine the focal length required for her glasses.
c)What kind of lenses are they (converging or diverging)?
d) Ophthalmologists use the unit “diopters”... which is 1/f (where f is in m). What is her prescription in diopters? (If her lenses are converging, the diopters are positive; if they are diverging the diopters are negative.)
e) Sketch a ray tracing of how her glasses will image a far - away object. It does need not need to be “to scale” (because unless you really scale it down, the object probably still would be off the page) but it should have all three principle rays.
f) Will the image be upright or inverted? Real or virtual? Enlarged or reduced?
g)Finally: What is her new near point with her glasses on? (In this case, you need to find what location images to my eye’s near point when my glasses are on ....and this is why I have bifocals!)
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