In the context of light curves, observations of an eclipsing binary system can directly tell astronomers not only the masses of its stars but also their _____
A) orbital periods
B) diameters
C) intensity of magnetic fields
D) temperatures
B
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A red razorback uniform appears red because
A. It refracts red wavelengths B. It creates constructive interference for red wavelengths C. It reflects red wavelengths D. It absorbs red wavelengths
A parallel plate capacitor with plate separation of 4.0 cm has a plate area of 4.0 × 10-2 m2. What is the capacitance of this capacitor with air between these plates?
A) 8.9 × 10-11 F B) 8.9 × 10-12 F C) 8.9 × 10-13 F D) 8.9 × 10-14 F E) 8.9 × 10-15 F
A wave generated in a medium is a longitudinal wave when
a. there is a net transport of matter by the wave. b. the molecules of the medium are unable to exert forces on each other. c. molecular displacements are parallel to the wave velocity. d. molecular displacements are perpendicular to the wave velocity. e. the density of the medium is less than the density of water.
At 20°C an aluminum ring has an inner diameter of 5.000 cm, and a brass rod has a diameter of 5.020 cm. Keeping the brass rod at 20°C, which of the following temperatures of the ring will allow the ring to just slip over the brass rod? (aAl = 2.4 × 10^-5 /°C, abrass = 1.9 × 10^-5/°C )
a. 111°C c. 228°C b. 187°C d. 437°C