Based on the graph, when was the maximum abundance of CO2 over the past 800,000 years?
A) about 300,000 years ago
B) about 125,000 years ago
C) 1750
D) now
D) now
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The conversion of mass to energy of other forms via nuclear fission is
A) less than 1%. B) about 10%. C) about 20%. D) about 30%. E) more than 30%.
Addition by 1. Components: The figure shows four vectors, 
, 
, 
, and 
, having magnitudes 10.0 m, 8.00 m, 6.00 m, and 2.00 m, respectively. Find the magnitude of the sum of these four vectors.
Fill in the blank(s) with the appropriate word(s).
Two sources emit beams of light of wavelength 550 nm. The light from source A has an intensity of 10 µW/m2,
and the light from source B has an intensity of 20 µW/m2. This is all we know about the two beams. Which of the following statements about these beams are correct? (There could be more than one correct choice.) A) Beam B carries twice as many photons per second as beam A. B) A photon in beam B has twice the energy of a photon in beam A. C) The frequency of the light in beam B is twice as great as the frequency of the light in beam A. D) A photon in beam B has the same energy as a photon in beam A. E) None of the above statements are true.
None of the pulsars emit pulses of visible light because
a. pulsars are too hot to emit visible light. b. pulsars contain black holes that won't let visible light escape. c. the gravitational field of a pulsar is so great that the visible light emitted is redshifted. d. pulsars are too far away for the visible light to be bright enough to be detected at Earth. e. A few pulsars do emit visible light pulses.