A person's hyperopic (farsighted) eye can focus on objects that are 75 cm away and farther. What power and what focal length contact lenses should be prescribed so this person can see objects 25 cm and farther from the eye?
What will be an ideal response?
2.7 diopters, 38 cm
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The induced electric and magnetic fields of Maxwell are
A) parallel to each other. B) perpendicular to each other. C) non-directional.
A horizontal metal bar rotates at a constant angular velocity w about a vertical axis through one of its ends while in a constant magnetic field B that is directed down. The emf induced between the two ends of the bar is
A) constant and proportional to the product B ?. B) constant and proportional to the product B ?2. C) constant and proportional to the product B2 ?2. D) variable with a maximum of B ?. E) variable with a maximum of B ?2.
If the nation's yearly total energy use and also the yearly gross national product [GNP] are graphed, the two graphs rise at the same rate until the mid-1970s, but they diverge from each other after about 1973
This divergence of the graphs shows that A) energy use increases when the nation's goods and services increase. B) U.S. energy efficiency decreased after 1973, due to lower energy prices. C) energy efficiency has played a large role in providing goods and services since 1973. D) as the price of goods and services decreases, energy use increases. E) an increasing GNP causes energy use to also increase.
The first solenoid has 2 times the diameter, 2 times the number of turns, and 2 times the length of the second solenoid. Which solenoid has the greater inductance and by what factor?
a. the first solenoid by a factor of 8 c. the first solenoid by a factor of 16 b. the second solenoid by a factor of 8 d. the second solenoid by a factor of 32