The two most abundant elements that make up the salinity of seawater are
A) sodium and potassium.
B) chlorine and sulfur.
C) calcium and sulfur.
D) chlorine and sodium.
Answer: D
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Thin Films: Light in a frozen block of ice reflects off the ice-air interface at the surface of the block. What phase shift does it undergo?
A. 0° B. 90° C. 180° D. 270° E. It does not undergo any phase shift.
What practical value did astronomy offer to ancient civilizations?
A) It helped them keep track of time and seasons, and it was used by some cultures for navigation. B) It allowed them to predict eclipses with great accuracy. C) It helped them understand our cosmic origins. D) It helped them find uses for ancient structures like Stonehenge.
Two beams of coherent light are shining on the same piece of white paper. With respect to the crests and troughs of such waves, darkness will occur on the paper where:
a. the crest from one wave overlaps with the crest from the other. b. the crest from one wave overlaps with the trough from the other. c. the troughs from both waves overlap. d. darkness cannot occur as the two waves are coherent.
If a solid has a half-filled valence band, which of the following would it be?
A. a conductor B. an insulator C. a semiconductor D. a p-type semiconductor E. an n-type semiconductor