When a beam of light that is traveling in air is reflected by a glass surface, there is
A) a 180° phase change in the reflected beam.
B) a 45° phase change in the reflected beam.
C) a 60° phase change in the reflected beam.
D) no phase change in the reflected beam.
E) a 90° phase change in the reflected beam.
A
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Scientists suspect that Mars once had abundant liquid water on its surface. For this to have been true, early Mars must have had ________ than Mars today.
A) a much higher atmospheric pressure and much stronger greenhouse effect B) a larger mass and radius C) a smaller axis tilt and less elliptical orbit D) larger polar caps and more dust storms
Do astronomers use ground-based X-ray telescopes?
A. No, because no astronomical objects emit X-rays. B. No, because X-rays cannot get through Earth's atmosphere. C. Yes, because they can penetrate gas clouds. D. No, because astronomers have not yet devised detectors for X-rays.
The study of minerals is called
a. paleontology. b. geology. c. mineralogy. d. petrology.
What is the upper limit of stars the unaided eye can discern on a moonless night in a rural area?
A) about 3000 B) about 30,000 C) about 300,000 D) about 3,000,000