You need 14 W of infrared laser light power with wavelength 1270 nm to bore a hole in a diamond. How many downward atomic transitions per second must occur in the laser if all of them result in light directed onto the diamond?
(c = 3.00 × 108 m/s, h = 6.626 × 10-34 J ? s)
A) 8.9 × 1019
B) 8.9 × 1018
C) 5.9 × 1019
D) 2.7 × 1018
Answer: A
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When we enlarge a photograph of an iron ring, the image of the hole becomes
A) smaller. B) larger. C) neither smaller nor larger.
A hot (70°C) lump of metal has a mass of 250 g and a specific heat of 0.25 cal/g•°C. John drops the metal into a 500-g calorimeter containing 40 g of water at 20°C. The calorimeter is constructed of a material that has a specific heat of 0.10 cal/ g•°C. When equilibrium is reached, what will be the final temperature? (cwater = 1.00 cal/g•°C.)
a. 114°C c. 40°C b. 72°C d. 37°C
Whose work with SETI lead to the discovery of pulsars in 1967?
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