The appearance of an aurora indicates that
A. the planet is being bombarded by small meteors.
B. there is intelligent life on the planet producing the aurora from below.
C. there is a lot of lightning discharges in the planet's atmosphere.
D. the planet has a magnetic field.
Answer: D
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A. in salt water B. in fresh water C. The buoyant force is the same in both cases.
A bar magnet moving with speed V passes below a stationary charge q. What can be said about the magnitude of the magnetic forces on the bar magnet (Fb) and on the charge q (Fq)
Sea level fluctuated several times during the Paleozoic. Which of the following is not a representative factor for sea level rise in the Paleozoic?
A) Melting of continental glaciers. B) Ocean basins stood high on the asthenosphere due to active seafloor spreading. C) Ocean basins stood high on the asthenosphere due to slow but continuous seafloor convergence. D) The breakup of the Precambrian supercontinent.
Thin Films: A soap bubble, when illuminated at normal incidence with light of 463 nm, appears to be especially reflective. If the index of refraction of the film is 1.35, what is the minimum thickness the soap film can be if it is surrounded by air?
Fill in the blank(s) with the appropriate word(s).