Suppose it turns out that one in 1 million stars has a planet that at some point in its history is home to an advanced civilization. Then the total number of civilizations that have arisen in our galaxy would be closest to ________
A) 40,000 B) 400,000 C) 40 D) 4,000 E) 400
B
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Most molecules found in the giant molecular clouds are based on silicon
Indicate whether the statement is true or false
The wavelength of a certain portion of an electromagnetic wave is 314 nm. What is its frequency and classification?
A) 9.55 × 1014 Hz, ultraviolet B) 9.55 × 1014 Hz, X-ray C) 8.44 × 1015 Hz, X-ray D) 9.55 × 1015 Hz, ultraviolet
When red light illuminates a grating with 7000 lines per centimeter, its second maximum is at 62.4°. What is the wavelength of this light?
What will be an ideal response?
Density: A porch roof that slopes upward at 45° measures 3.0 m × 5.0 m. It is covered with a slab of insulating material that is 2.0 cm thick. If the density of the insulation is 15 kg/m3, what is the weight of the insulation, in pounds, on the roof? (1.00 kg weighs 2.2 lb and density is mass per unit volume.)
A. 4.5 lb B. 9.0 lb C. 20 lb D. 990 lb E. 9.9 lb