The cosmic background radiation
a. has a blackbody spectrum.
b. has its peak emission in the microwave band.
c. corresponds to a blackbody at a temperature of 2.726 kelvins.
d. all of the above
a
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Radio waves travel at the speed of light, 300,000 km/s. The wavelength of a radio wave received at 100 megahertz is
A) 0.3 m. B) 3.0 m. C) 30 m. D) 300 m. E) none of the above
An object attached to the end of a string swings in a vertical circle (R = 1.2 m), as shown. At an instant when ? = 30°, the speed of the object is 5.1 m/s and the tension in the string has a magnitude of 20 N. What is the mass of the object?
A. 2.0 kg B. 1.5 kg C. 1.8 kg D. 1.2 kg E. 0.80 kg
Our Sun will likely undergo a nova event in about 5 billion years
Indicate whether the statement is true or false
Movement of air aloft can influence surface air pressure; sometimes air aloft piles up—it converges—causing the surface air pressure to
A) increase and surface winds to blow away from the center of highest pressure. B) decrease and surface winds to blow away from the center of high pressure. C) increase and surface winds to blow away from the center of low pressure. D) decrease and surface winds to blow away from the center of lowest pressure.