Betelgeuse is a red supergiant star in the constellation Orion. It radiates heat at the rate of 2.70 × 1030 W and has a surface temperature of 3000 K. Assuming that it is a perfect emitter, what is the radius of Betelgeuse?
The Stefan-Boltzmann constant is 5.670 × 10-8 W/m2 · K4.
A) 7.80 × 1010 m
B) 8.70 × 1010 m
C) 1.40 × 1011 m
D) 1.90 × 1011 m
E) 2.16 × 1011 m
Answer: E
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Light passes from medium one 
to medium two 
If v1< v2 then at the boundary
A. f increases 
decreases.
B. f does not change, 
increases.
C. f decreases, 
increases.
D. f does not change, 
decreases.
The speed of light is 3.0 × 10^5 km/s, and it takes 1.3 s for light to travel from the Moon to Earth. From this information, what is the distance to the Moon?
a. 390,000 km b. 230,000 km c. 3.9 km d. 2.3 km e. 4.3 × 10^5 km
The nearest star to the Sun is Sirius
Indicate whether the statement is true or false
Coulomb's Law: As shown in the figure, charge q1 = 2.2 × 10-6 C is placed at the origin and charge q2 = -3.30 × 10-6 C is placed on the x-axis, at x = -0.200 m. Where along the x-axis can a third charge Q = -8.30 × 10-6 C be placed so that the resultant force on Q is zero?
Fill in the blank(s) with the appropriate word(s).