Why do astronomers often measure the visible-light apparent brightness instead of the total apparent brightness of a star?
A) All stars put out most of their light in the visible range of the spectrum.
B) In order to measure the total apparent brightness of a star, you must measure its brightness in all wavelengths, and this is difficult to do. The only wavelengths you can measure from the surface of Earth are visible and radio wavelengths.
C) Most stars do not put out light in other ranges of the spectrum.
D) They are identical for most stars.
E) Astronomers are lazy.
B
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The amount of oxygen in Earth's atmosphere has gradually grown over the last few billion years.
Answer the following statement true (T) or false (F)
The Schwarzschild radius of a 1- black hole is approximately
a. 3 km.
b. 1,500,000 km, the size of the Sun
c. 150,000,000 km or 1 AU.
d. 3 x 1013 km or 1 pc.
Atmosphere pressure on mars is roughly half that of Earth's at sea level
Indicate whether the statement is true or false.
A solid cylinder (I = MR2/2) has a string wrapped around it many times. When I release the cylinder, holding on to the string, the cylinder falls and spins as the string unwinds. What is the downward acceleration of the cylinder as it falls?
a. 0 c. 6.5 m/s2 b. 4.9 m/s2 d. 9.8 m/s2