A college professor can see objects clearly only if they are between 70 and 500 cm from her eyes. Her optometrist prescribes bifocals (Fig. 25.23) that enable her to see distant objects through the top half of the lenses and read students’ papers at a distance of 25 cm through the lower half. What are the respective powers of the top and bottom lenses?
Answer to relevant QuestionsA senior citizen wears bifocals (Fig. 25.23) in which the top half of the lens has a focal length of – 0.850 and the bottom half of the lens has a focal length of + 0.500. What are this person’s near point and far point? A person is prescribed with contact lenses that have powers of – 3.0 D. What type of lenses are these? What is the lenses’ focal length? What is the maximum magnification of a magnifying glass with a power of + 3.0 D for (a) A person with a near point of 25 cm and (b) A person with a near point of 10 cm? Two lenses of focal length 0.45 cm and 0.35 cm are available for a compound microscope using an eyepiece of focal length of 3.0 cm, and the distance between the lenses has to be 15 cm. (a) Which lens should be used as the ...A telescope has an angular magnification of – 50 x and a barrel 1.02 m long. What are the focal lengths of the objective and the eyepiece?
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