According to the following figure, about how long ago did oxygen reach its current abundance in Earth's atmosphere?
a. 3 billion years ago
b. 1 billion years ago
c. 0.5 billion years ago
d. 0.25 billion years ago
e. 0.1 billion years ago
d. 0.25 billion years ago
Physics & Space Science
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Atoms can be excited by
A) thermal agitation. B) electron impact. C) photon impact. D) all of the above E) none of the above
Physics & Space Science
Light in a transparent material that has an index of refraction of 1.333 strikes the boundary with another transparent material for which the index of refraction is 1.010
What is the critical angle for total internal reflection between these two materials?
Physics & Space Science
What is the hardness of quartz on the Mohs scale?
a. 1 b. 4 c. 7 d. 10
Physics & Space Science
If ? = 9.0 V, what is the current in the 15-? resistor?
a.
0.20 A
b.
0.30 A
c.
0.10 A
d.
0.26 A
Physics & Space Science