A radioisotope placed near a radiation detector registers 80 counts per second. Eight hours later the detector registers 5 counts per second. What is the half-life of the radioisotope?
What will be an ideal response?
Two hours. Since 80 halved 4 times is 5, there have been four half-life periods in the 8 h, and 8 h/4 = 2 h.
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Which of the following natural processes would have to occur for water in the oceans to become fresh water available for human use?
A) Evaporation and infiltration B) Transpiration, purification, and precipitation C) Precipitation and infiltration D) Evaporation and precipitation
During photosynthesis, ________
A) sugars and carbon dioxide are produced B) there is a net consumption of oxygen and carbon dioxide C) there is a net consumption of water and carbon dioxide D) carbon dioxide and oxygen are produced
What evidence suggests that Mars had an active hydrologic cycle in the past?
What will be an ideal response?
The cP air mass of North America is usually associated with a source region in:
a. Iceland. b. Aleutian Islands. c. Mexico. d. Canada.