One light-year is the distance light travels in one year. The speed of light is about 300,000 km/s . How far is 1 light-year?
A) 1.08 billion km (1,080,000,000, or 1.08 109 km)
B) 300 thousand km (300,000, or 3 105 km)
C) 9.46 trillion km (9,460,000,000,000, or 9.46 1012 km)
D) 18 million km (18,000,000, or 1.8 107 km)
Question 2
What eventually halts the gravitational collapse of an interstellar gas cloud that forms an object that is massive enough to become a star?
A) the central object becoming hot enough to sustain nuclear fusion in its core
B) a critical fraction of the gas has been driven further into space
C) nothing; all collapsing gas clouds become black holes
D) the crowding of electrons in the core
The rapid speed of cAMP production
Absorption of ultraviolet light by aromatic amino acids
Parallel Light Rays from Distant Objects
Interactions of Light and Matter
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