The place where light is brought into focus (to form an image) in the human eye is called the
A) retina.
B) optic nerve.
C) lens.
D) pupil.
E) cornea.
A) retina.
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A proton (1.67 × 10-27 kg) is accelerated to 99.8% the speed of light. How much energy did the accelerator have to impart?
A) 14.8 GeV B) 13.9 GeV C) 38.9 GeV D) 7.52 GeV E) 223. GeV
Why do sunspots appear dark in pictures of the Sun?
A) They are too cold to emit any visible light. B) They are holes in the solar surface through which we can see through to deeper, darker layers of the Sun. C) They are extremely hot and emit all their radiation as X-rays rather than visible light. D) They actually are fairly bright, but appear dark against the even brighter background of the surrounding photosphere.
Which event marks the beginning of a supernova?
A) the expansion of a low-mass star into a red giant B) the beginning of neon burning in an extremely massive star C) the onset of helium burning after a helium flash in a star with mass comparable to that of the Sun D) the sudden collapse of an iron core into a compact ball of neutrons E) the sudden outpouring of X-rays from a newly formed accretion disk
Which of the following has been established through helioseismology observations?
A) The Sun's magnetic field is generated by the dynamo effect at the bottom of the convection zone deep under the photosphere. B) Magnetic fields are observed on Earth because of the presence of an ionized atmosphere. C) When seen through the naked eye, prominences look black because of emission in the three hydrogen Lyman series lines. D) Solar flares are found to occur in regions where identically directed magnetic fields meet.