A 35-mm camera equipped with a 45-mm focal length lens is used to photograph a tree 15 m tall. If the aperture of the lens is set at f/2, what is the aperture diameter?
A) 14 mm B) 18 mm C) 32 mm D) 23 mm E) 27 mm
D
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The primary evidence for an accelerating Universe comes from observations of young stars in the Milky Way.
A.) True, observations show that there were many more young, massive stars in the early Universe. B.) True, massive star supernovae allow us to measure the expansion rate of the Universe. C.) False, in order to measure accelerating expansion, we need to measure the distances of objects billions of light-years away. D.) False, evidence for an accelerating Universe comes from observations of the oldest stars in the Milky Way, white dwarfs. E.) False, we have to look at young stars in other galaxies beyond the Milky Way to measure the acceleration of the Universe.
Which is heaviest?
A) oxygen atom B) hydrogen atom C) electron D) proton E) water molecule
Radioactive decay is involved in
a. irradiating food to destroy harmful bacteria. b. keeping the interior of the Earth hot. c. making smoke detectors work. d. finding flaws in jet engine parts. e. all of the above.
Two capacitors with capacitances of 1.0 mF and 0.50 mF, respectively, are connected in series. The system is connected to a 50-V battery. What electrical potential energy is stored in the 1.0-mF capacitor?
a. 5.6 × 10^-4 J c. 0.065 × 10^-3 J b. 4.3 × 10^-3 J d. 1.4 × 10^-4 J