A machinist with normal vision has a near point at 25 cm. This machinist wears +4.25-diopter eyeglasses in order to do very close work
With these eyeglasses, what is the near point of the machinist? Assume that he wears the glasses extremely close to his eyes. A) 12 cm
B) 10 cm
C) 7 cm
D) 15 cm
E) 17 cm
A
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The operation of a microwave oven makes use of
A) the polar nature of water molecules. B) flip flopping of polarized molecules. C) an oscillating electric field. D) all of the above E) none of the above
Suppose Earth were to cool down a little. How would the carbon dioxide cycle tend to restore temperatures to normal?
A) Cooler temperatures cause volcanoes to become more active, so they release more carbon dioxide into the atmosphere than they do when temperatures are warmer. B) Cooler temperatures allow carbon dioxide to form rain and rain out of the atmosphere. C) Cooler temperatures mean more ice and more erosion, which somehow makes the planet warm up. D) Cooler temperatures lead to slower formation of carbonate minerals in the ocean, so carbon dioxide released by volcanism builds up in the atmosphere and strengthens the greenhouse effect.
A thin infinitely large current sheet lies in the y-z plane. Current of magnitude Js per unit length along the z axis travels in the y-axis direction, which is up out of the page. Which diagram below correctly represents the direction of the magnetic field on either side of the sheet?
A.
B.
C.
D.
E.
According to Kepler's laws, Halley's Comet circles the Sun in an elliptical path with the Sun at one focus of the ellipse. What is it that Kepler's laws indicate is at the other focus of the ellipse?
a. nothing b. the Earth c. The comet itself passes through the other focus. d. The tail of the comet stays at the other focus.